Ground-Water Resources in the

Black Hills Area, South Dakota

Water-Resources Investigations Report 03-4049

Prepared in cooperation with the Bureau of Reclamation,

South Dakota Department of Environment and Natural Resources,

and the West Dakota Water Development District

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

U.S. Geological Survey

Ground-Water Resources in the

Black Hills Area, South Dakota

By Janet M. Carter and Daniel G. Driscoll, U.S. Geological Survey, and

J. Foster Sawyer, South Dakota Department of Environment and Natural Resources

Water-Resources Investigations Report 03-4049

Prepared in cooperation with the Bureau of Reclamation,

South Dakota Department of Environment and Natural Resources,

and the West Dakota Water Development District
U.S. Department of the Interior

GALE A. NORTON, Secretary

U.S. Geological Survey

Charles G. Groat, Director

The use of firm, trade, and brand names in this report is for identification purposes only

and does not constitute endorsement by the U.S. Government.

Rapid City, South Dakota: 2003

For additional information write to:

District Chief

U.S. Geological Survey

1608 Mt. View Road

Rapid City, SD 57702

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286
Contents III

CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Ground-Water Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Description of Study Area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Ground Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Availability of Ground-Water Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Characteristics of Major Aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

General Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Ground-Water Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Characteristics of Minor Aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Water Quality of Ground-Water Resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

General Characteristics for Major Aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

General Characteristics for Minor Aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Ground-Water Quality Relative to Water Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

FIGURES

1. Schematic diagram showing (A) porosity and permeability; and (B) aquifers and

confining beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Map showing area of investigation for the Black Hills Hydrology Study. . . . . . . . . . . . . . . . . . . . . . 3

3. Graph showing long-term trends in precipitation for the Black Hills area,

water years 1931-98. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. Stratigraphic column for the Black Hills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

5. Map showing distribution of hydrogeologic units in the Black Hills area . . . . . . . . . . . . . . . . . . . . . 5

6. Geologic cross section A-A′ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

7. Schematic diagram showing simplified hydrologic setting of the Black Hills area . . . . . . . . . . . . . . 7

8. Boxplots showing distribution of well yields from selected aquifers . . . . . . . . . . . . . . . . . . . . . . . . . 9

9-13. Maps showing depth to top of:

9. Deadwood Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

10. Madison Limestone. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

11. Minnelusa Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

12. Minnekahta Limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

13. Inyan Kara Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

14-18. Maps showing generalized thickness of:

14. Deadwood Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

15. Madison Limestone and Englewood Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

16. Minnelusa Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

17. Minnekahta Limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

18. Inyan Kara Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

19-23. Map showing potentiometric surface of:

19. Deadwood aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

20. Madison aquifer and locations of major artesian springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

21. Minnelusa aquifer and locations of major artesian springs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

22. Minnekahta aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

23. Inyan Kara aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

24. Map showing saturated thickness of the Madison aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

25. Map showing saturated thickness of the Minnelusa aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

26. Selected hydrographs illustrating trends in ground-water levels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

27. Map showing water temperature in the Madison aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

28. Map showing specific conductance in the Madison aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

29. Map showing specific conductance in the Minnelusa aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

30. Map showing specific conductance in the Inyan Kara aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

31. Graph showing relation between dissolved solids and well depth for Madison aquifer . . . . . . . . . . . 30

32. Boxplots showing hardness for selected aquifers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

33. Map showing hardness in the Inyan Kara aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

34. Map showing sulfate concentrations in the Minnelusa aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

35. Map showing radon concentrations in the Deadwood aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

TABLE

1. Summary of the characteristics of major aquifers in the study area . . . . . . . . . . . . . . . . . . . . . . . . . . 8
IV Contents

CONVERSION FACTORS, VERTICAL DATUM, AND WELL-NUMBERING SYSTEM

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F - 32) / 1.8

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929).

OTHER ABBREVIATIONS, ACRONYMS, AND SYMBOLS USED

Multiply By To obtain

acre-foot 1,233 cubic meter 

acre-foot 0.001233 cubic hectometer 

foot 0.3048 meter

gallons per minute 0.06309 liter per second

inch 2.54 centimeter

inch 25.4 millimeter

mile 1.609 kilometer

square mile 259.0 hectare

square mile 2.590 square kilometer 

mg/L

μg/L

pCi/L

milligrams per liter

micrograms per liter

picocuries per liter

GWSI

USEPA

MCL

SMCL

USGS

Ground Water Site Inventory database

U.S. Environmental Protection Agency

Maximum Contaminant Level

Secondary Maximum Contaminant Level

U.S. Geological Survey

Boxplots are a useful and concise graphical display for summarizing the distribution of a data set. Two different 

types of boxplots are used in this report. In both types, the center of the data (known as the median) is shown as 

the center line of the box. The variation or spread of the data (known as the interquartile range) is shown by the 

box height. 

Maximum

90th percentile

75th percentile

Mean

Median

25th percentile

10th percentile

Minimum

The first type is a truncated boxplot, and is used for all 

boxplots that do not show water-quality data. In the 

truncated boxplot, the whiskers are drawn only to the 

90th and 10th percentiles of the data set. Thus, 

values included in the largest 10 percent and the 

smallest 10 percent of the data are not shown. The 

mean, maximum, and minimum values for the data 

set are shown.

Outlier data value more than 3 times the 

interquartile range outside the quartile

Outlier data value less than or equal to 3 and 

more than 1.5 times the interquartile range 

outside the quartile

Data value less than or equal to 1.5 times

the interquartile range outside the quartile

75th percentile

Median

25th percentile

Data value less than or equal to 1.5 times the 

interquartile range outside the quartile

The second type is a standard boxplot, and is used for 

all boxplots that show water-quality data. In the 

standard boxplot, the whiskers are drawn only to the 

last data value that is within 1.5 times the 

interquartile range (height of the box). Values 

outside 1.5 times the interquartile range are called 

“outliers.” For water-quality data, these outliers are 

of interest when comparing to water-quality 

standards and general distribution of extreme values.

Spring

Water table

•

°

*

×

°

°∼
Introduction 1

Ground-Water Resources in the

Black Hills Area, South Dakota

By Janet M. Carter and Daniel G. Driscoll, U.S. Geological Survey, and

J. Foster Sawyer, South Dakota Department of Environment and Natural Resources

ABSTRACT

The availability of ground-water 

resources in the Black Hills area is influenced by many factors including location, 

local recharge and ground-water flow 

conditions, and structural features. Thus, 

the availability of ground water can be 

extremely variable throughout the Black 

Hills area, and even when water is available, it may not be suitable for various 

uses depending on the water quality. 

The major bedrock aquifers in the 

Black Hills area are the Deadwood, 

Madison, Minnelusa, Minnekahta, and 

Inyan Kara aquifers. Minor bedrock 

aquifers occur in other hydrogeologic 

units, including confining units, due to 

fracturing and interbedded permeable 

layers. 

Various information and maps are 

presented in this report that describe availability and quality of ground-water 

resources in the Black Hills area. However, there is no guarantee of obtaining 

usable water at any location due to the 

extreme potential variability in conditions 

that can affect the availability and quality 

of ground water in the area. Maps presented in this report include the distribution of hydrogeologic units; depth to the 

top of the five formations that contain 

major aquifers; thickness of the five formations that contain major aquifers; 

potentiometric maps for the five major 

aquifers; saturated thickness of the Madison and Minnelusa aquifers; water temperature in the Madison aquifer; specific 

conductance in the Madison, Minnelusa, 

and Inyan Kara aquifers; hardness in the 

Inyan Kara aquifer; sulfate concentrations 

in the Minnelusa aquifer; and radon concentrations in the Deadwood aquifer. 

Water quality of the major aquifers 

generally is very good in and near outcrop 

areas but deteriorates progressively with 

distance from the outcrops. In the Minnelusa aquifer, an abrupt increase in concentrations of dissolved sulfate occurs 

downgradient from outcrop areas, where a 

zone of active anhydrite dissolution 

occurs. 

Most limitations for the use of 

ground water are related to aesthetic qualities associated with hardness and high 

concentrations of chloride, sulfate, 

sodium, manganese, and iron. Very few 

health-related limitations exist for ground 

water; most limitations are for radionuclides, such as radon and uranium. In 

addition, high concentrations of arsenic 

have been measured in a few samples 

from the Minnelusa aquifer.

INTRODUCTION

Ground water originating in the Black 

Hills area is used for municipal, industrial, 

agricultural, and recreational purposes 

throughout much of western South Dakota. 

The Black Hills area is an important recharge 

area for aquifers in the northern Great Plains. 

About 45 percent of the recent population 

growth in the Black Hills area has occurred in 

unincorporated areas where water-supply 

systems are not provided by municipalities 

(Carter and others, 2002). Adequate water 

supplies for various uses can be difficult to 

obtain at some locations in the Black Hills 

area.

The Black Hills Hydrology Study was 

conducted by the U.S. Geological Survey 

(USGS) during 1990-2002 to assess the 

quantity, quality, and distribution of water 

resources within the Black Hills area. The 

Black Hills Water Management Study was a 

companion study conducted by the Bureau of 

Reclamation during 1992-2002 to evaluate 

alternatives for management of water 

resources in the area. Information summarized in this report was initially assembled in 

conjunction with these two studies. This 

report was produced in cooperation with the 

Bureau of Reclamation, South Dakota 

Department of Environment and Natural 

Resources, and West Dakota Water Development District.

The purpose of this report is to describe 

ground-water resources in the Black Hills 

area. Availability and quality of water in the 

major aquifers (Deadwood, Madison, Minnelusa, Minnekahta, and Inyan Kara) and 

various minor aquifers in the Black Hills area 

are described. Information collected and 

compiled from both the Black Hills 

Hydrology Study and the Black Hills Water 

Management Study that relates to the availability of ground water in the Black Hills area 

is presented in this report. Specifically, this 

report contains maps showing: (1) distribution of hydrogeologic units; (2) depth to the 

top of the five formations that contain major 

aquifers; (3) thickness of the five formations 

that contain major aquifers; (4) potentiometric maps for the five major aquifers; 

(5) saturated thickness of the Madison and 

Minnelusa aquifers; (6) water temperature in 

the Madison aquifer; (7) specific conductance in the Madison, Minnelusa, and Inyan 

Kara aquifers; (8) hardness in the Inyan Kara 

aquifer; (9) sulfate concentrations in the 

Minnelusa aquifer; and (10) radon concentrations in the Deadwood aquifer. More detailed 

information regarding ground-water 

resources in the Black Hills area was summarized by Carter and others (2002) and 

Driscoll and others (2002) from a series of 

previous topical reports.
2 Ground-Water Resources in the Black Hills Area, South Dakota

GROUND-WATER PROCESSES

Precipitation falling on the earth’s surface generally infiltrates into the soil horizon, 

unless the soil is saturated or the infiltration 

capacity is exceeded. As water infiltrates into 

the ground, some of it clings to particles of 

soil or to roots of plants just below the land 

surface. Water not used by plants can move 

deeper into the ground through spaces or 

cracks in the soil, sand, or rocks, until it 

reaches a water table or a confining unit (such 

as clay or shale). The top of the water in the 

soil, sand, or rocks (top of the saturated zone) 

is called the water table, and the water that 

fills the spaces and cracks is called ground 

water. A confining unit is a relatively lowpermeability layer of rock through which 

water cannot easily move. After reaching the 

water table or confining unit, the water then 

fills the spaces (voids) and cracks above the 

water table or above the confining unit.

The process of infiltration of water 

from the land surface to ground water is 

called recharge. Ground water is recharged 

from rain water and snowmelt or from water 

that leaks through the bottom of some lakes 

and streams. Water can be discharged from an 

aquifer by pumping from a well or by flowing 

naturally from a spring. An aquifer is the 

underground soil or rock through which 

ground water can easily move and which 

supplies usable quantities of water to wells or 

springs. An aquifer may be only a few feet 

thick to hundreds of feet thick; it may lie a 

few feet below the land surface to thousands 

of feet below; it may underlie just a few acres 

or as much as thousands of square miles. 

Rock materials may be classified as 

consolidated or unconsolidated. Consolidated rocks (often called bedrock) may 

consist of limestone, dolomite, sandstone, 

siltstone, shale, or granite. Unconsolidated 

rock consists of granular material such as 

sand, gravel, silt, and clay. The amount of 

ground water that can flow through soil or 

rock depends on the size of the spaces in the 

soil or rock and how well the spaces are connected. Porosity is the percentage of the soil 

or rock volume that is occupied by pore 

space, which is void of material. Permeability 

is the measure of how well the spaces are 

connected (fig. 1A). An estimated one million cubic miles of the world’s ground water 

is stored within one-half mile below the land 

surface (U.S. Geological Survey, 1994).

Consolidated rock may contain fractures, small cracks, pore spaces, spaces 

between layers, and solution openings—all 

of which can hold water and may be connected. Vertical fractures may intersect horizontal openings, enabling water to move from 

one layer to another. Water can dissolve 

carbonate rocks, such as limestone, to form 

solution openings through which water can 

move both horizontally and vertically. Caves, 

such as Wind Cave and Jewel Cave (two of 

the largest caves in the world; fig. 2), are 

examples of large solution openings. 

Figure 1. Schematic diagram showing (A) porosity and permeability (modified from Clark and Briar, 1993); and

(B) aquifers and confining beds (modified from Heath, 1983).

Aquifers and confining beds

Porosity and permeability

B

A

Fracture Fracture racture

Water-table

well

Artesian

well

UNCONFINED

AQUIFER

CONFINING

BED

CONFINED

AQUIFER

UNSATURATED

ZONE

SATURATED ZONE

Land surface

SAND Capillary Capillary

fringe

Potentiometric Potentiometric

surface surface

SAND

Solution olution

opening opening LIMESTONE LIMESTONE

Capillary

fringe

Potentiometric

surface

Water table Water table ater table Well

screen

Well

screen

Artesian pressure Artesian pressure Artesian pressure

Solution

opening LIMESTONE

CLAY

Water-filled

pores

HIGH

PERMEABILITY

(water can

easily flow)

LOW

PERMEABILITY

(water cannot

easily flow)

Water-filled

fractures or

solution openings

UNCONSOLIDATED MATERIAL ROCK
Description of Study Area 3

Figure 2. Area of investigation for the Black Hills Hydrology Study.

N. Fork Rapid Cr

Belle Fourche Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Cold

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Redbird

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Beaver

Spring

C s

reek

Creek Canyon

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

Butte

x

Ellsworth

Air Force

Base

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

0 10 20

0 10 20 MILES

KILOMETERS

APPROXIMATE EXTENT OF THE BLACK

 HILLS AREA, REPRESENTED BY

 GENERALIZED OUTER EXTENT OF 

 THE OUTCROP OF THE INYAN KARA

 GROUP (modified from Strobel and others,

 1999)

OUTCROP OF MADISON LIMESTONE

 (from Strobel and others, 1999)

OUTCROP OF MINNELUSA FORMATION

 (from Strobel and others, 1999)

SOUTH DAKOTA

Area

shown

Black

Hills

EXPLANATION

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Missouri River

Oahe

Reservoir

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

Unconsolidated materials in the Black 

Hills area generally consist of sand and 

gravel, boulders, silt, or clay deposited by 

streams or in lakes. Alluvial deposits (alluvium) generally are adjacent to streams in the 

flood plain. Well-sorted unconsolidated 

material can store large quantities of ground 

water. The coarser materials—sand and 

gravel—readily yield water to wells.

Ground water can occur in aquifers 

under two different conditions. Where watertable conditions occur, water does not fill the 

formation containing aquifer material all the 

way to the top and the aquifer is considered 

unconfined. Where an aquifer is completely 

filled with water (fully saturated) and is overlain by a confining unit, the water can be confined under pressure and can rise above the 

top of the aquifer in an artesian well to a level 

representing the potentiometric surface. In 

the schematic shown in figure 1B, the potentiometric surface of the confined (artesian) 

aquifer is higher than the water table of the 

unconfined aquifer overlying the confined 

aquifer. Artesian wells will flow where the 

potentiometric surface is above the land 

surface. Semiconfining units contain some 

layers with low permeability but may 

transmit some water to and from adjacent 

aquifers.

DESCRIPTION OF STUDY AREA

The study area (fig. 2) consists of the 

topographically defined Black Hills and adjacent areas located in western South Dakota. 

The Black Hills are situated between the 

Cheyenne and Belle Fourche Rivers. The 

study area includes most of the larger communities in western South Dakota and 

contains about one-fifth of the State’s population.

Outcrops of the Madison Limestone 

and Minnelusa Formation, which are areas 

where these geologic formations occur at the 

land surface, are shown in figure 2. The generalized outer extent of the outcrop of the 

Inyan Kara Group, which approximates the 

outer extent of the Black Hills area, also is 

shown in figure 2.

Climate

The overall climate of the Black Hills 

area is continental, which is characterized 

generally by low precipitation amounts, hot 

summers, cold winters, and extreme variations in both precipitation and temperatures. 

Local climatic conditions are affected by 

topography, with generally lower temperatures and higher precipitation at the higher 

altitudes.
4 Ground-Water Resources in the Black Hills Area, South Dakota

Long-term trends in precipitation for 

water years 1931-98 for the study area are 

shown in figure 3; a water year is the 12-

month period, October 1 through 

September 30, and is designated by the calendar year in which it ends. Annual precipitation for the study area averaged 18.61 inches 

and has ranged from 10.22 inches in water 

year 1936 to 27.39 inches in water year 1995 

(Driscoll, Hamade, and Kenner, 2000). 

Figure 3. Long-term trends in precipitation for the 

Black Hills area, water years 1931-98.

0

30

10

20

ANNUAL PRECIPITATION,

IN INCHES

Annual precipitation

Long-term average

 (18.61 inches)

1930 200 1940 1950 1960 1970 1980 1990 0

WATER YEAR

Geology

Throughout geologic time, the Black 

Hills area has experienced frequent periods of 

inundation by seas, extended erosion, mountain building, and intrusion by igneous rocks; 

thus, the geology of the study area is very 

complex. The Black Hills uplift formed as an 

elongated dome about 60 to 65 million years 

ago. Numerous structural features, such as 

folds and fractures, were created by the deformation and displacement of rocks during the 

uplift. Pairs of large anticlines (folds in which 

the strata dip away from the axis like an arch) 

and synclines (folds in which the strata dip 

toward the axis like a trough) occur on the 

northern and southern flanks of the Black 

Hills and plunge away from the uplift into the 

surrounding plains. Numerous smaller anticlines, synclines, and domes, along with 

numerous faults and monoclines, occur 

throughout the Black Hills area. Igneous 

intrusions, such as Bear Butte, were 

emplaced on the northern flanks of the uplift 

during the Tertiary period.

The geologic time scale is divided into 

four eras and spans from the Precambrian Era 

(earliest) to the Cenozoic Era (latest). A 

stratigraphic column, which portrays the 

vertical (or chronological) sequence of geologic units of the Black Hills, is shown in 

figure 4. The geologic units are grouped into 

stratigraphic intervals representing hydrogeologic units comprising various aquifers, 

confining units, and semiconfining units, as 

shown in the explanation for figure 5. 

Figure 5 shows outcrops of the hydrogeologic units and locations of numerous structural features in the study area.

The oldest geologic units in the study 

area are the Precambrian-age crystalline 

(igneous and metamorphic) rocks, which are 

exposed in the central core of the Black Hills 

(fig. 5). Surrounding the Precambrian-age 

crystalline core is a layered series of sedimentary rocks including limestones, sandstones, and shales that are exposed in roughly 

concentric rings around the uplifted flanks of 

the Black Hills, as shown in figure 5. The 

bedrock sedimentary units generally dip 

away from the flanks of the Black Hills as 

shown in the geologic cross section (fig. 6), 

which shows the geologic units in a vertical cut along the line A-A′ in figure 5. Following are descriptions for the Paleozoic- and 

Mesozoic-age sedimentary units in the Black 

Hills area.

Figure 4. Stratigraphic column for the Black Hills.

GEOLOGIC UNIT DESCRIPTION THICKNESS

IN FEET

ABBREVIATION

FOR

STRATIGRAPHIC

INTERVAL

ERATHEM SYSTEM

QUATERNARY

& TERTIARY (?)

UNDIFFERENTIATED ALLUVIUM, TERRACES

AND COLLUVIUM 0-50 Sand, gravel, boulders, and clay.

1,200-2,700

Tw WHITE RIVER GROUP Light colored clays with sandstone channel fillings and local limestone lenses. 

TERTIARY

QTac

Principal horizon of limestone lenses giving teepee buttes. 

Dark-gray shale containing scattered concretions. 

Widely scattered limestone masses, giving small teepee buttes. 

Black fissile shale with concretions. 

PIERRE SHALE

NIOBRARA FORMATION 180-300 Impure chalk and calcareous shale.

CARLILE SHALE 1350-750

Light-gray shale with numerous large concretions and sandy layers.

Dark-gray shale.

GRANEROS GROUP

GREENHORN FORMATION

Kps

225-380 Impure slabby limestone. Weathers buff.

Dark-gray calcareous shale, with thin Orman Lake limestone at base.

BELLE FOURCHE SHALE

MOWRY SHALE

MUDDY

SANDSTONE

NEWCASTLE

SANDSTONE

SKULL CREEK SHALE

150-850

Gray shale with scattered limestone concretions.

Clay spur bentonite at base.

125-230

0-150

Light-gray siliceous shale. Fish scales and thin layers of bentonite.

Brown to light-yellow and white sandstone.

150-270 Dark-gray to black siliceous shale.

CRETACEOUS

FALL RIVER FORMATION

INYAN KARA

GROUP

10-200 Massive to thin-bedded, brown to reddish-brown sandstone.

Yellow, brown, and reddish-brown massive to thinly bedded sandstone, pebble conglom- 35-700 erate, siltstone, and claystone. Local fine-grained limestone and coal.

0-220

0-225

Green to maroon shale. Thin sandstone.

Massive fine-grained sandstone.

250-450

0-45

Greenish-gray shale, thin limestone lenses.

Glauconitic sandstone; red sandstone near middle.

Red siltstone, gypsum, and limestone.

MORRISON FORMATION

LAKOTA FORMATION

UNKPAPA SS

SUNDANCE

FORMATION

GYPSUM SPRING FORMATION

Kik

Ju JURASSIC

SPEARFISH FORMATION T Ps R TRIASSIC

MINNEKAHTA LIMESTONE

Po OPECHE SHALE

Pmk

375-800

125-65

Red silty shale, soft red sandstone and siltstone with gypsum and thin limestone layers.

Gypsum locally near the base.

Thin to medium-bedded, fine grained, purplish-gray laminated limestone.

125-150 Red shale and sandstone.

1375-1,175

1<200-1,000

30-60

10-235

10-150

10-500

Yellow to red cross-bedded sandstone, limestone, and anhydrite locally at top.

Red shale with interbedded limestone and sandstone at base.

Massive light-colored limestone. Dolomite in part. Cavernous in upper part.

Pink to buff limestone. Shale locally at base.

Buff dolomite and limestone.

Green shale with siltstone.

Massive to thin-bedded brown to light-gray sandstone. Greenish glauconitic shale, flaggy

 dolomite, and flat-pebble limestone conglomerate. Sandstone, with conglomerate

 locally at the base.

Schist, slate, quartzite, and arkosic grit. Intruded by diorite, metamorphosed

 to amphibolite, and by granite and pegmatite.

PERMIAN

PENNSYLVANIAN

MISSISSIPPIAN

P Pm MINNELUSA FORMATION

MADISON (PAHASAPA) LIMESTONE

ENGLEWOOD FORMATION

MDme

Ou

DEVONIAN

WHITEWOOD (RED RIVER) FORMATION

WINNIPEG FORMATION

DEADWOOD FORMATION

UNDIFFERENTIATED IGNEOUS AND

METAMORPHIC ROCKS

OCd

pCu

ORDOVICIAN

CAMBRIAN

PRECAMBRIAN

PALEOZOIC

MESOZOIC

CENOZOIC

Modified from information furnished by the Department of Geology and Geological Engineering,

South Dakota School of Mines and Technology (written commun., January 1994)

0-300

Tui INTRUSIVE IGNEOUS ROCKS Includes rhyolite, latite, trachyte, and phonolite. --

1 Modified based on drill-hole data

Interbedded sandstone, limestone, dolomite, shale, and anhydrite.
Description of Study Area 5

Figure 5. Distribution of hydrogeologic units in the Black Hills area (modified from Strobel and others, 1999).

QTac

Tw

Tui

Kps

Ju

TRPs

MDme

Kik

Pmk

Po

Ou

PPm

OCd

pCu

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Redbird

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Canyon

Springs

Beaver Creek

Creek

Cold

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

A

A'

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

Alluvium, terraces, and

 colluvium, undifferentiated

Unconsolidated

units

White River

aquifer

Minnekahta

aquifer

Minnelusa

aquifer

Madison

aquifer

Deadwood

aquifer

Inyan Kara

aquifer

Tertiary

intrusive

units

Spearfish

confining

unit

Opeche

confining

unit

Cretaceoussequence

confining

unit

Jurassicsequence

semiconfining 

unit

Ordoviciansequence

semiconfining

unit

Precambrian

aquifer

White River Group

Undifferentiated intrusive

 igneous rocks

Pierre Shale to Skull Creek

 Shale, undifferentiated

Inyan Kara Group

Morrison Formation to

 Gypsum Spring Formation,

 undifferentiated

Spearfish Formation

Minnekahta Limestone

Opeche Shale

Minnelusa Formation

Madison (Pahasapa) Lime-

 stone and Englewood

 Formation

Whitewood Formation and

 Winnipeg Formation

Deadwood Formation

Undifferentiated igneous

 and metamorphic rocks

STRATIGRAPHIC

UNITS

MAP UNITS

HYDROGEOLOGIC

UNITS

A A' LINE OF GEOLOGIC SECTION

FAULT—Dashed where approxi-

 mated. Bar and ball on down-

 thrown side

ANTICLINE—Showing trace of axial

 plane and direction of plunge.

 Dashed where approximated

SYNCLINE—Showing trace of axial

 plane and direction of plunge.

 Dashed where approximated

MONOCLINE—Showing trace of

 axial plane. Dashed where

 approximated

DOME—Symbol size approximately

 proportional to size of dome.

 Dome asymmetry indicated by

 arrow length

104o 45' 103o

30'

15' 103o

30'

44o45'

15'

44o

45'

30'

43o

15'

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
6 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 6. Geologic cross section A-A′ (modified from Strobel and others, 1999). Location of section is shown in figure 5. Abbreviations for stratigraphic intervals are 

explained in figure 4.

0

1,000

2,000

3,000

4,000

5,000

6,000

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

FEET

A A'

7,000

FEET

MDme

MDme

Kps

Ju Kik

PPm

PPm

OCd

OCd Pmk Po QTac QTac

Rapid Creek Rapid Creek

South Fork Castle Creek

South Fork Castle Creek

Rapid Creek

Rapid Creek

Rapid City

Rapid Creek

0

0 4 2

2 4 6 8 10 MILES

6 10 KILOMETERS 8

VERTICAL EXAGGERATION X5

VERTICAL DATUM IS NGVD OF 1929

T Ps R

SOUTH DAKOTA

WYOMING

pCu pCu

LIMESTONEPLATEAU

WEST EAST

The oldest sedimentary unit in the study 

area is the Cambrian- and Ordovician-age 

Deadwood Formation, which is composed 

primarily of brown to light-gray sandstone, 

shale, limestone, dolomite, and local basal 

conglomerate (Strobel and others, 1999). 

In the northern and central Black Hills, the 

Deadwood Formation is overlain by 

Ordovician-age rocks, which include the 

Whitewood and Winnipeg Formations. In the 

southern Black Hills, where the Whitewood 

and Winnipeg Formations are absent, the 

Deadwood Formation is overlain by the 

Englewood Formation, which generally is 

present throughout the Black Hills area 

except in the crystalline core. The Englewood 

Formation is overlain by the Madison Limestone.

The Mississippian-age Madison Limestone is a massive, gray to buff limestone with 

some dolomite (Strobel and others, 1999). 

The Madison Limestone was deposited by 

shallow seas and subsequently was exposed 

at land surface for approximately 50 million 

years. During this period of extensive erosion, rainwater, made slightly acidic during 

its passage through the air, infiltrated slowly 

down through the limestone, dissolving the 

limestone and forming caves in the rocks 

(Gries, 1996). The process of dissolving mineral and rock materials is called dissolution. 

As the caves collapsed, many of them broke 

through to the land surface, creating sinkholes. This process is called karstification, 

which results in a type of topography (with 

caves and sinkholes) called karst. Numerous 

caves and fractures occur within the upper 

part of the Madison Limestone (Peter, 1985). 

The Madison Limestone is overlain by the 

Minnelusa Formation.

The Pennsylvanian- and Permian-age 

Minnelusa Formation consists mostly of 

yellow to red sandstone, limestone, dolomite, 

and shale (Strobel and others, 1999). In addition to sandstone and dolomite, the middle 

part of the formation contains anhydrite, 

which can be easily dissolved by water, and 

shale (DeWitt and others, 1986). The upper 

part of the Minnelusa Formation also may 

contain anhydrite, which generally has been 

dissolved in or near the outcrop areas, occasionally forming collapse features. The 

Minnelusa Formation is overlain by the 

Opeche Shale, which is overlain by the 

Minnekahta Limestone.

The Permian-age Minnekahta Limestone is a fine-grained, purple to gray laminated limestone (Strobel and others, 1999). 

The Minnekahta Limestone is overlain by the 

Spearfish Formation.

The Spearfish Formation is a red, silty 

shale with interbedded red sandstone and siltstone (Strobel and others, 1999). Massive 

gypsum deposits are scattered throughout the 

Spearfish Formation. Because gypsum is 

easily dissolved by water, numerous sinkholes in the Spearfish Formation have 

developed, especially in the northern Black 

Hills (Epstein, 2000). Overlying the 

Spearfish Formation are Mesozoic-age units 

that are composed primarily of shale, siltstone, and sandstone deposits. These units 

include the Cretaceous-age Inyan Kara 

Group.

The Inyan Kara Group consists of the 

Lakota Formation and overlying Fall River 

Formation. A resistant ridge of Cretaceousage sandstones, mostly of the Lakota Formation, completely encircles the Black Hills and 

stands hundreds of feet above the surrounding prairie. This ridge, known as the 

Cretaceous hogback, forms the general 

boundary between the Black Hills and the 

prairie (Gries, 1996). The Lakota Formation 

consists of yellow, brown, and reddishbrown, massive to thinly bedded sandstone, 

pebble conglomerate, siltstone, and claystone 

that were deposited by rivers (Gott and 

others, 1974); locally there are lenses of limestone and coal. The Fall River Formation is a 

brown to reddish-brown, fine-grained sandstone, thin bedded at the top and massive at 

the bottom (Strobel and others, 1999). The 

Inyan Kara Group is overlain by a thick 

sequence of various shale units with some 

interbedded sandstone and limestone units.

Ground Water

The hydrologic setting of the Black 

Hills area is schematically illustrated in 

figure 7. The major bedrock aquifers are the 

Deadwood, Madison, Minnelusa, Minnekahta, and Inyan Kara aquifers. Minor bedrock aquifers occur in other units, including 

confining units, due to fracturing and interbedded permeable layers. In general, groundwater flow in these aquifers is radially away 

from the central core of the Black Hills. The 

bedrock aquifers primarily receive recharge 

from infiltration of precipitation on outcrops, 

and the Madison and Minnelusa aquifers also 

receive substantial recharge from streamflow 

losses. The unconsolidated units, which 

include alluvium, terraces, and colluvium, 

are considered aquifers where saturated. 

Alluvial deposits along streams commonly 

are used as local aquifers.

Many of the sedimentary units contain 

aquifers, both within and beyond the study 

area. Within the Paleozoic-age rock interval, 

aquifers in the Deadwood Formation, 

Madison Limestone, Minnelusa Formation, 

and Minnekahta Limestone are used extensively. The aquifers are collectively confined 

by the underlying Precambrian-age rocks and 

the overlying Spearfish Formation. Individually, these aquifers are separated by minor 

confining layers or by low-permeability 

layers within the individual units. Extremely 

variable leakage can occur between these 

aquifers (Peter, 1985; Greene, 1993). 

Confined (artesian) conditions generally exist within the bedrock aquifers in locations where an upper confining layer is 

present except in areas close to the formation 

outcrop. Under confined conditions, water in 

a well will rise above the top of the aquifer in 

which it is completed. Flowing wells will 

result when drilled in areas where the potentiometric surface (level to which water will 

rise) is above the land surface. Flowing wells 

and artesian springs that originate from 

confined aquifers are common around the 

periphery of the Black Hills.

The Precambrian-age basement rocks 

generally have low permeability and form the 

lower confining unit for the series of sedimentary aquifers (fig. 7). However, localized 

aquifers occur in many locations in the crystalline core of the Black Hills where secondary permeability (developed after the 

rock was formed) has resulted from weathering and fracturing. Water-table (unconfined) conditions generally occur in these 

localized aquifers, and topography can 

strongly influence ground-water flow directions. 
Availability of Ground-Water Resources 7

Figure 7. Schematic diagram showing simplified hydrologic setting of the Black Hills area. Schematic diagram generally corresponds with geologic cross 

section shown in figure 5.

Deadwood

Madison

Inyan Kara

Group Formation

Limestone

Precambrian igneous and

metamorphic rocks

Dip of sedimentary rocks exaggerated.

Relative thickness NOT to scale.

Limestone

Minnekahta

Minnelusa

Madison

Limestone

Formation

Formation

Deadwood

Minnelusa

Formation

Alluvial

aquifer

Potentiometric

surface of the

Madison

aquifer Spring

conduit

Water

table

Cave

Flowing well

LIMESTONE

PLATEAU

MAJOR AQUIFER

CONFINING UNIT

SPRING

EXPLANATION

Overlying the Precambrian-age rocks is 

the Deadwood aquifer, which is contained 

within the Deadwood Formation and is used 

primarily near outcrop areas. Regionally, the 

Precambrian-age rocks act as an underlying 

confining unit to the Deadwood aquifer, and 

the Whitewood and Winnipeg Formations, 

where present, act as overlying semiconfining units (Strobel and others, 1999). 

Where the Whitewood and Winnipeg Formations are absent, the Deadwood aquifer is in 

contact with the overlying Englewood 

Formation, which is considered similar in 

hydrologic characteristics to the lower 

Madison Limestone.

The Madison aquifer generally occurs 

within the karstic upper part of the Madison 

Limestone, where numerous fractures and 

solution openings have created extensive secondary porosity and permeability. The entire 

Madison Limestone and Englewood Formation were included in the delineation of the 

Madison aquifer for this study. Thus, in this 

report, outcrops of the Madison Limestone 

and Englewood Formation (fig. 5) are 

referred to as the outcrop of the Madison 

Limestone for simplicity. The Madison 

aquifer receives recharge from streamflow 

losses and precipitation on the outcrop. Lowpermeability layers in the lower part of the 

Minnelusa Formation generally act as an 

upper confining unit to the Madison aquifer. 

However, collapse related to karst features in 

the top of the Madison Limestone and fracturing related to the Black Hills uplift may 

have reduced the effectiveness of the overlying confining unit in some locations.

The Minnelusa aquifer occurs within 

layers of sandstone, dolomite, and anhydrite 

in the lower portion of the Minnelusa 

Formation and sandstone and anhydrite in the 

upper portion. Shales in the lower portion of 

the Minnelusa Formation act as confining 

layers to the underlying Madison aquifer; 

however, the extent of hydraulic separation 

between the two aquifers varies greatly 

between locations and is not well defined. 

Collapse breccia associated with dissolution 

of interbedded anhydrite in the Minnelusa 

Formation may enhance secondary porosity 

to the aquifer (Long and others, 1999). The 

Minnelusa aquifer receives substantial 

recharge from streamflow losses and precipitation on the outcrop. Streamflow recharge to 

the Minnelusa aquifer generally is less than to 

the Madison aquifer because much streamflow is lost to the Madison aquifer before 

reaching the outcrop of the Minnelusa 

Formation. The Minnelusa aquifer is confined by the overlying Opeche Shale.

The Madison and Minnelusa aquifers 

are distinctly different aquifers, but are connected hydraulically in some areas. Many of 

the artesian springs have been interpreted as 

originating at least partially from upward 

leakage from the Madison aquifer; however, 

the overlying Minnelusa aquifer and other 

aquifers probably contribute to artesian 

springflow in many locations. Although the 

confining layers in the lower parts of the 

Madison and Minnelusa aquifers generally 

do not transmit water at a high rate, their 

capacity to store water could influence how 

these aquifers respond to stress (Long and 

Putnam, 2002).

The Minnekahta aquifer, which overlies 

the Opeche Shale, is contained within the 

Minnekahta Limestone. The Minnekahta 

aquifer typically is very permeable, but well 

yields can be limited by the small aquifer 

thickness. The Minnekahta aquifer receives 

recharge primarily from precipitation on the 

outcrop and some additional recharge from 

streamflow losses. The overlying Spearfish 

Formation acts as a confining unit to the 

Minnekahta aquifer and to other aquifers in 

the underlying Paleozoic-age rock interval. 

Hence, most of the artesian springs occur 

near the outcrop of the Spearfish Formation.

Within the Mesozoic-age rock interval, 

the Inyan Kara aquifer is used extensively, 

and aquifers in various other formations are 

used locally. The Inyan Kara aquifer receives 

recharge primarily from precipitation on the 

outcrop. The Inyan Kara aquifer also may 

receive recharge from leakage from aquifers 

in the underlying Paleozoic-age rock interval 

(Swenson, 1968; Gott and others, 1974). As 

much as 4,000 feet of Cretaceous-age shales 

act as the upper confining unit to aquifers in 

the Mesozoic-age rock interval.

AVAILABILITY OF GROUND-WATER 

RESOURCES

The availability of ground-water 

resources in the Black Hills area is influenced 

by many factors including location, local 

recharge and ground-water flow conditions, 

and structural features. Thus, the availability 

of ground water can be extremely variable 

throughout the Black Hills area. The suitability of available water supplies also can be 

limited by water quality, as discussed later in 

this report. This section of the report provides 

information and maps that describe potential 

availability of ground-water resources in the 

Black Hills area. Readers are cautioned that 
8 Ground-Water Resources in the Black Hills Area, South Dakota

there is no guarantee of obtaining usable 

water at any location due to the extreme 

potential variability in conditions that can 

affect the availability and quality of ground 

water in the area.

Characteristics of Major Aquifers

General descriptions of aquifer characteristics and ground-water levels, with 

emphasis on the major aquifers, are presented 

in this section of the report. A series of maps 

showing the depth and thickness of selected 

geologic formations, and the potentiometric 

surface and saturated thickness of selected 

aquifers, also is presented.

General Characteristics

Aquifer characteristics, including area, 

thickness, and storage volume, are presented 

in table 1 for the major aquifers in the study 

area. Aquifer characteristics for the Precambrian aquifer also are presented with the 

major aquifers because numerous wells are 

completed in this aquifer in the crystalline 

core of the Black Hills.

Localized aquifers occur in the igneous 

and metamorphic rocks that make up the 

crystalline core of the Black Hills and are 

referred to collectively as the Precambrian 

aquifer. The Precambrian aquifer is not continuous and ground-water conditions are controlled mainly by secondary permeability 

caused by fracturing and weathering. The 

aquifer is considered to be contained in the 

area where the Precambrian-age rocks are 

exposed in the central core, which has an area 

of approximately 825 square miles in the 

study area. The thickness of the Precambrian 

aquifer has been estimated by Rahn (1985) to 

be generally less than 500 feet, which was 

considered the average saturated thickness 

for calculations of the estimated amount of 

recoverable water in storage (table 1). Wells 

in the Custer area have been completed at 

depths greater than 1,000 feet, indicating that 

localized aquifers are thicker in some locations. The Precambrian aquifer is mostly 

unconfined, but may have locally confined 

conditions.

Large amounts of water are stored 

within the major aquifers, but not all of it is 

recoverable because some of the water is contained in unconnected pore spaces. Thus, 

effective porosity, which is the porosity of a 

rock that consists of interconnected voids, 

was used in estimating the amount of recoverable water in storage (table 1). Where 

aquifer units are not fully saturated (generally 

in and near outcrop areas), the saturated 

thickness is less than the formation thickness 

and the aquifer is unconfined. For the 

Madison and Minnelusa aquifers, it was possible to delineate the saturated thickness of 

the unconfined portions of these aquifers, as 

discussed later in this report. Average saturated thicknesses of the unconfined and confined portions of the Madison and Minnelusa 

aquifers were used in storage estimates for 

these aquifers. For the other major aquifers, 

full saturation was assumed because more 

detailed information was not available.

The total volume of recoverable water 

stored in the major aquifers (including the 

Precambrian aquifer) within the study area is 

estimated as 256 million acre-feet, which is 

slightly more than 10 times the maximum 

storage of Oahe Reservoir, a large reservoir 

on the Missouri River northeast of the study 

area (fig. 2). Although the volume of stored 

ground water is very large, the water quality 

may not be suitable for all uses in some parts 

of the study area, as discussed in a following 

section of this report. The largest storage 

volume is for the Inyan Kara aquifer because 

of the large effective porosity (0.17). Storage 

in the Minnelusa aquifer is larger than in the 

Madison aquifer, primarily because of larger 

average saturated thickness.

Well yields (fig. 8) for wells completed 

in the major aquifers were obtained from the 

USGS Ground Water Site Inventory (GWSI) 

database. The mean well yields for the aquifers generally are much higher than the 

median well yields because some well yields 

are very high. Well yields generally are lower 

for wells completed in the Precambrian 

aquifer than for the major aquifers (fig. 8) 

because the Precambrian aquifer is not continuous and most of the available water is 

stored in fractures. The Madison aquifer has 

the potential for high well yields, and the 

mean well yield is higher in the Madison 

aquifer than the other major aquifers. The 

Minnelusa aquifer also has the potential 

for high well yields. The Deadwood and 

Minnekahta aquifers could have well yields 

as high as 1,000 gallons per minute in localized areas. Low well yields are possible in 

some locations for all the major aquifers.

Maps showing estimated depths to tops 

of formations that contain the major aquifers 

(Deadwood, Madison, Minnelusa, Minnekahta, and Inyan Kara) are presented in 

figures 9-13. The depths shown are to the top 

of the formations, which are not necessarily 

the depths to the tops of the water-bearing 

layers. In fact, water-bearing layers in any 

given formation may be minimal or absent at 

many locations, especially in areas on or near 

the outcrops. Readers are cautioned that relatively large errors in estimated depths can 

occur because of large potential uncertainties 

in estimated altitudes for tops of formations 

especially in areas with limited well and testhole data.

Maps showing generalized thicknesses 

of the formations that contain major aquifers 

are presented in figures 14-18. Thicknesses 

shown are estimated formation thicknesses 

and are not necessarily indicative of saturated 

thicknesses at any given location. In fact, the 

formations may have little saturation or may 

even be dry at many locations, especially in 

areas on or near outcrops. Readers are again 

cautioned that relatively large errors in estimated thicknesses can occur.

Maps showing estimated potentiometric surfaces for the major aquifers are presented in figures 19-23. The potentiometric 

contours on the maps show the approximate 

altitude to which water would rise in tightly 

cased, nonpumping wells. In general, the 

direction of ground-water flow is perpendicular to the potentiometric contours and in the 

direction of the hydraulic gradient (water 

flows from higher hydraulic head to lower 

hydraulic head). In general, ground-water 

flow in the major aquifers is radially outward 

from the uplifted area. However, structural 

features, such as folds and faults, and other 

factors may have sufficiently large local 

influences on ground-water flow directions. 

Flow directions may be nearly parallel to 

potentiometric contours in some locations, 

especially in the Madison aquifer (Long, 

2000). Readers are again cautioned that 

relatively large errors in mapped potentiometric contours can occur due to insufficient 

data.

1From Rahn (1985).

2Storage estimated by multiplying area times average saturated thicknesses times effective porosity.

3The area used in storage calculation was the area of the exposed Precambrian-age rocks, which is 825 square miles.

4Average saturated thickness of the confined area of the Madison aquifer. The unconfined area had an average saturated thickness of 300 feet.

5Storage values are the summation of storage in the confined and unconfined areas.

6Average saturated thickness of the confined area of the Minnelusa aquifer. The unconfined area had an average saturated thickness of 142 feet.

Table 1. Summary of the characteristics of major aquifers in the study area

[--, no data]

Aquifer Area

(square miles)

Maximum

formation

thickness

(feet)

Average

saturated

thickness

(feet)

Effective

porosity1

Estimated amount

of recoverable

water in storage2

(million acre-feet)

Precambrian 35,041 -- 1500 0.01 2.6

Deadwood 4,216 500 226 .05 30.5

Madison 4,113 1,000 4521 .05 562.7

Minnelusa 3,623 1,175 6736 .05 570.9

Minnekahta 3,082 65 50 .05 4.9

Inyan Kara 2,512 900 310 .17 84.7

Combined storage for major aquifers 256.3
Availability of Ground-Water Resources 9

Figure 8. Distribution of well yields from selected aquifers (data obtained from U.S. Geological Survey Ground 

Water Site Inventory database).

561 137 166 433 64 246

Precambrian Deadwood Madison Minnelusa Minnekahta Inyan

Kara

AQUIFER

0.01

10,000

0.02

0.05

0.1

0.2

0.5

1

2

5

10

20

50

100

200

500

1,000

2,000

5,000

WELL YIELD, IN GALLONS PER MINUTE

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

561 Number of wells with

 yield data

Minimum

Maximum

Mean *

*

* *

*

*

*

Maps showing estimated saturated 

thicknesses of the unconfined areas of the 

Madison and Minnelusa aquifers are shown 

in figures 24 and 25, respectively. Both the 

Madison and Minnelusa aquifers are unconfined in and near outcrop areas, but generally 

are confined (fully saturated) at some distance away from outcrops. In general, saturated thicknesses are estimated as less than 

200 feet for most outcrop areas. These areas 

may be especially susceptible to water-level 

fluctuations resulting from drought conditions, and these formations may be predominantly dry in many of these areas regardless 

of precipitation conditions. In most areas, the 

Madison and Minnelusa aquifers are fully 

saturated within a short distance downgradient of the outcrops. However, in the southwest part of the study area, neither aquifer is 

fully saturated for a distance of about 6 miles 

downgradient of the respective outcrops.

Ground-Water Levels

Daily water-level data were collected 

for 71 observations wells for the Black Hills 

Hydrology Study. Hydrographs for these 

wells through water year 1998 were presented by Driscoll, Bradford, and Moran 

(2000). Hydrographs for four of these wells 

are presented in figure 26 to illustrate the 

fluctuations in water levels that can occur in 

bedrock aquifers in the Black Hills area. For 

the hydrographs presented in this report, solid 

lines indicate continuous records and dashed 

lines indicate periods with discontinuous 

records, which may be based only on periodic 

manual measurements in some cases.

Water levels can be affected by several 

factors including pumping of nearby wells 

and climatic conditions. Long-term waterlevel declines could have various effects, 

including changes in ground-water flow 

patterns, reduction in springflow, increased 

pumping costs, and dry wells. A large percentage of the observations wells completed 

in the Madison and Minnelusa aquifers 

respond quickly to climatic conditions. 

Nearly all of the hydrographs for these aquifers (Driscoll, Bradford, and Moran, 2000) 

show a downward water-level trend prior to 

1993, as illustrated in the example hydrographs for a well pair completed in the 

Madison and Minnelusa aquifers (fig. 26A). 

This downward trend can be partially attributed to dry climatic conditions in the Black 

Hills area during this period. Precipitation 

amounts generally were above average after 

1993 (fig. 3), and water levels increased rapidly (fig. 26A). In general, there is very little 

indication of long-term water-level declines 

from ground-water withdrawals in any of the 

bedrock aquifers in the Black Hills area 

(Carter and others, 2002), as shown by the 

long-term hydrograph for the Redwater 

Minnelusa well (fig. 26B). 

Of the hydrographs for the 71 observation wells presented by Driscoll, Bradford, 

and Moran (2000), the Reptile Gardens 

Madison well showed the largest water-level 

fluctuation of about 111 feet (fig. 26C). 

Larger water-level fluctuations at other locations in the Black Hills area may be possible. 

Such fluctuations could result in dry wells or 

reduced pumping capacity during periods of 

declining water levels.

Characteristics of Minor Aquifers

In addition to the major aquifers, many 

other aquifers are used in the study area. The 

Newcastle Sandstone, White River Group, 

and the unconsolidated units are considered 

to contain aquifers where saturated (Strobel 

and others, 1999). In addition, many of the 

semiconfining and confining units shown in 

figure 5 may contain local aquifers. This section of the report provides a brief overview 

from Strobel and others (1999) of other aquifers in the study area that are contained in 

various units from oldest to youngest.

The Whitewood Formation, where 

present, can contain a local aquifer that 

seldom is used because of generally more 

reliable sources in the adjacent Madison or 

Deadwood aquifers. Local aquifers can exist 

in the Spearfish confining unit where gypsum 

and anhydrite have been dissolved, causing 

increased porosity and permeability; these 

aquifers are referred to as the Spearfish 

aquifer in this report. The Jurassic-sequence 

semiconfining unit consists of shales and 

sandstones. Overall, this unit is semiconfining because of the low permeability of the 

interbedded shales; however, local aquifers 

exist in some formations such as the Sundance and Morrison Formations. These aquifers are referred to as the Sundance and 

Morrison aquifers in this report. 

The Cretaceous-sequence confining 

unit mainly includes shales of low permeability, such as the Pierre Shale; local aquifers 

in the Pierre Shale are referred to as the Pierre 

aquifer in this report. Within the Graneros 

Group, the Newcastle Sandstone contains an 

important minor aquifer referred to as the 

Newcastle aquifer. Because water-quality 

characteristics (discussed in a subsequent 

section of this report) are very different 

between the Newcastle aquifer and the other 

units in the Graneros Group, data are presented for the Newcastle aquifer separately 

from the other units in the Graneros Group, 

known as the Graneros aquifer in this 

report.

Tertiary intrusive units are present only 

in the northern Black Hills, and generally are 

relatively impermeable, although “perched” 

ground water often is associated with intrusive sills. The White River aquifer consists of 

various discontinuous units of sandstone and 

channel sands along the eastern flank of the 

Black Hills; local aquifers can exist where 

saturated conditions occur. Unconsolidated 

units of Tertiary or Quaternary age, including 

alluvium, terraces, colluvium, and windblown deposits, all have the potential to be 

local aquifers where they are saturated.
10 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 9. Depth to top of Deadwood Formation.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

OUTCROP OF DEADWOOD

 FORMATION (from Strobel

 and others, 1999)

DEADWOOD FORMATION ABSENT

 (from Carter and Redden, 1999e)

DEPTH TO TOP OF DEADWOOD

 FORMATION, IN FEET (from

 Jarrell, 2000a)

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Less than 200

5,000 to 5,500

5,500 to 6,000

6,000 to 6,500

No data

200 to 400

400 to 600

600 to 800

800 to 1,000

1,000 to 1,500

1,500 to 2,000

2,000 to 2,500

2,500 to 3,000

3,000 to 3,500

3,500 to 4,000

4,000 to 4,500

4,500 to 5,000

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 11

Figure 10. Depth to top of Madison Limestone.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Redbird

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

OUTCROP OF MADISON

 LIMESTONE

MADISON LIMESTONE ABSENT

 (from Carter and Redden,

 1999d)

DEPTH TO TOP OF MADISON

 LIMESTONE, IN FEET (from

 Jarrell, 2000b)

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Less than 200

5,000 to 5,500

5,500 to 6,000

6,000 to 6,500

No data

200 to 400

400 to 600

600 to 800

800 to 1,000

1,000 to 1,500

1,500 to 2,000

2,000 to 2,500

2,500 to 3,000

3,000 to 3,500

3,500 to 4,000

4,000 to 4,500

4,500 to 5,000

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
12 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 11. Depth to top of Minnelusa Formation.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

OUTCROP OF MINNELUSA

 FORMATION

MINNELUSA FORMATION ABSENT

 (from Carter and Redden, 1999c)

DEPTH TO TOP OF MINNELUSA

 FORMATION, IN FEET (from

 Jarrell, 2000c)

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Less than 200

200 to 400

400 to 600

600 to 800

800 to 1,000

1,000 to 1,500

1,500 to 2,000

2,000 to 2,500

2,500 to 3,000

3,000 to 3,500

3,500 to 4,000

4,000 to 4,500

4,500 to 5,000

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 13

Figure 12. Depth to top of Minnekahta Limestone.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Redbird

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

OUTCROP OF MINNEKAHTA

 LIMESTONE (from Strobel

 and others, 1999) 

MINNEKAHTA LIMESTONE ABSENT

 (from Carter and Redden, 1999b)

DEPTH TO TOP OF MINNEKAHTA

 LIMESTONE, IN FEET (from

 Jarrel, 2000d)

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Less than 200

200 to 400

400 to 600

600 to 800

800 to 1,000

1,000 to 1,500

1,500 to 2,000

2,000 to 2,500

2,500 to 3,000

3,000 to 3,500

3,500 to 4,000

4,000 to 4,500

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
14 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 13. Depth to top of Inyan Kara Group.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

OUTCROP OF INYAN KARA

 GROUP (from Strobel and

 others, 1999)

INYAN KARA GROUP ABSENT

 (from Carter and Redden,

 1999a)

DEPTH TO TOP OF INYAN KARA

 GROUP, IN FEET (from Jarrell,

 2000e)

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Less than 200

No data

200 to 400

400 to 600

600 to 800

800 to 1,000

1,000 to 1,500

1,500 to 2,000

2,000 to 2,500

2,500 to 3,000

3,000 to 3,500

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 15

Figure 14. Generalized thickness of the Deadwood Formation.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

OUTCROP OF DEADWOOD

 FORMATION

DEADWOOD FORMATION ABSENT

Less than 100

THICKNESS OF DEADWOOD

 FORMATION, IN FEET (from

 Carter and others, 2002) 

100 to 200

200 to 300

300 to 400

400 to 500

Greater than 500

No data

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
16 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 15. Generalized thickness of the Madison Limestone and Englewood Formation.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

MADISON LIMESTONE ABSENT

Less than 200

THICKNESS OF MADISON 

 LIMESTONE AND ENGLEWOOD

 FORMATION, IN FEET (from

 Galloway, 2000)

OUTCROP OF MADISON

 LIMESTONE

200 to 400

400 to 600

600 to 800

800 to 1,000

No data

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 17

Figure 16. Generalized thickness of the Minnelusa Formation.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

Less than 200

THICKNESS OF MINNELUSA

 FORMATION, IN FEET (from

 Jarrell, 2000f)

MINNELUSA FORMATION ABSENT

OUTCROP OF MINNELUSA

 FORMATION

200 to 400

400 to 600

600 to 800

800 to 1,000

Greater than 1,000

No data

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
18 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 17. Generalized thickness of the Minnekahta Limestone.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

Less than 50

THICKNESS OF MINNEKAHTA

 LIMESTONE, IN FEET (from

 Carter and others, 2002)

MINNEKAHTA LIMESTONE ABSENT

OUTCROP OF MINNEKAHTA

 LIMESTONE

Greater than 50

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 19

Figure 18. Generalized thickness of the Inyan Kara Group.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

OUTCROP OF INYAN KARA

 GROUP

INYAN KARA GROUP ABSENT

Less than 200

THICKNESS OF INYAN KARA

 GROUP, IN FEET

200 to 300

300 to 400

400 to 500

Greater than 500

No data

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
20 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 19. Potentiometric surface of the Deadwood aquifer.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo

Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peakx

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

4,400 4,600

5,000

5,200

5,400

4,800

5,800

5,600

5,200

5,000

5,400 5,800

5,000

5,800

6,000

6,000

5,800

6,000

6,200

6,000

6,000

4,800

6,000 6,200

4,600

3,800

4,800

4,000

4,400

4,600

4,200

3,600

6,400

3,400 3,200

6,400

3,800

4,000

4,000

3,800

5,000

4,200

4,400

4,800

4,600

4,400

4,000

EXPLANATION

OUTCROP OF DEADWOOD

 FORMATION

DEADWOOD FORMATION ABSENT

DEADWOOD FORMATION

 PRESENT, BUT OVERLAIN BY

 SURFICIAL DEPOSITS (from

 Carter and Redden, 1999e)

POTENTIOMETRIC CONTOUR—

 Shows altitude at which water

 would have stood in tightly

 cased, nonpumping wells

 (modified from Strobel and

 others, 2000e). Contour interval

 200 feet. Dashed where inferred.

 Vertical datum is NGVD of 1929

FAULT—Dashed where approx-

 imated. Bar and ball on

 downthrown side

ANTICLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

SYNCLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

MONOCLINE—Showing trace

 of axial plane. Dashed

 where approximated

DOME—Symbol size approx-

 imately proportional to size

 of dome. Dome asymmetry

 indicated by arrow length

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 21

Figure 20. Potentiometric surface of the Madison aquifer and locations of major artesian springs.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo

Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

3,700

3,600

5,800

5,800

4,800

4,800

4,400

6,600

3,600

6,400

3,500

3,400

3,800

3,800

4,200

4,000

4,200

4,400

5,000

5,200

5,200

4,800

3,200

5,400

5,400

5,600

5,600

4,600

4,400

6,000

6,000

6,200

4,200

4,200

6,400

4,000

4,400

6,400

3,400

3,800

3,600

3,800

4,200

2,600

4,000

2,800

2,800

3,000

3,000

6,600

6,600

6,000

6,400

6,200

5,500

5,000

4,500

3,600

4,000

3,900

3,700 3,800

3,200

3,600

3,500

4,600

3,400

3,400

3,800

3,900

3,800

3,700

3,000

Cool Spring

Hot Brook Spring

Cascade Springs

Beaver

Creek

Spring

Battle Creek

Spring

Evans Plunge Spring

Elk Creek Springs

Cleghorn/

Jackson

Springs

City Springs

Higgins Gulch

Spring

Old Spearfish

Hatchery Cox

Lake

Mirror

Lake and

McNenny

Rearing

Pond

Grace Coolidge

Creek Spring

EXPLANATION

OUTCROP OF MADISON

 LIMESTONE

MADISON LIMESTONE ABSENT

POTENTIOMETRIC CONTOUR—

 Shows altitude at which water

 would have stood in tightly cased,

 nonpumping wells (modified from

 Strobel and others, 2000d).

 Contour interval 100, 200, or 500

 feet, where appropriate. Dashed

 where inferred. Vertical datum is

 NGVD of 1929

MADISON LIMESTONE PRESENT,

 BUT OVERLAIN BY SURFICIAL

 DEPOSITS (from Carter and

 Redden, 1999d)

FAULT—Dashed where approx-

 imated. Bar and ball on 

 downthrown side

ANTICLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

SYNCLINE—Showing trace of

 axial plane and direction

 of plunge. Dashed where

 approximated

MONOCLINE—Showing trace of

 axial plane. Dashed where

 approximated

DOME—Symbol size approxi-

 mately proportional to size

 of dome. Dome asymmetry

 indicated by arrow length

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

ARTESIAN SPRING—Tail

 indicates direction of flow

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
22 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 21. Potentiometric surface of the Minnelusa aquifer and locations of major artesian springs.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo

Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

4,000

4,200

6,600

6,200

3,400

6,000

5,400

5,800

5,000 5,200

4,400

4,200

2,800

3,600

3,600

3,400

4,000

3,200

3,000

4,400

4,600

3,800

4,800

4,200

5,000

4,000

3,800

3,600

6,000

6,200

6,400

6,400

3,800

6,800

6,600

3,800

6,000

6,400

6,200

6,200

5,600

5,800

6,000

2,800

3,000

3,200

5,400

3,800

3,800

4,800

4,600

4,800

3,600

4,600

3,400

4,200

4,400

4,000

4,000

3,600

2,600

2,800

3,000

3,200

3,400

3,000

Cool Spring

Hot Brook Spring

Cascade Springs

Beaver

Creek

Spring

Battle Creek

Spring

Evans Plunge Spring

Elk Creek Springs

Cleghorn/

Jackson

Springs

City Springs

Higgins Gulch Spring

Cox Old Spearfish Hatchery

Lake

Mirror

Lake and

McNenny

Rearing

Pond

Grace Coolidge

Creek Spring

EXPLANATION

OUTCROP OF MINNELUSA

 FORMATION

MINNELUSA FORMATION

 ABSENT

MINNELUSA FORMATION

 PRESENT, BUT OVERLAIN

 BY SURFICIAL DEPOSITS

 (from Carter and Redden,

 1999c)

POTENTIOMETRIC CONTOUR—

 Shows altitude at which water

 would have stood in tightly cased,

 nonpumping wells (modified from

 Strobel and others, 2000c).

 Contour interval 200 feet. Dashed

 where inferred. Vertical datum is

 NGVD of 1929 

FAULT—Dashed where approx-

 imated. Bar and ball on

 downthrown side

ANTICLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

SYNCLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

MONOCLINE—Showing trace

 of axial plane. Dashed

 where approximated

DOME—Symbol size approx-

 imately proportional to size

 of dome. Dome asymmetry

 indicated by arrow length

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

ARTESIAN SPRING—Tail

 indicates direction of flow

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 23

Figure 22. Potentiometric surface of the Minnekahta aquifer.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo 

Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

3,900

4,500

3,600

3,500

3,600 3,500

3,700

3,800

3,600

3,800

3,900

3,400

3,500

3,600

3,300

3,700

3,600

3,100

3,200

3,800 3,500

3,400

3,700

3,300

3,600

3,300

3,400

3,500

3,800

3,800

3,800

3,500

3,600

3,400

3,400

3,800

3,700

3,000

EXPLANATION

OUTCROP OF MINNEKAHTA

 LIMESTONE

MINNEKAHTA LIMESTONE

 ABSENT

MINNEKAHTA LIMESTONE

 PRESENT, BUT OVERLAIN BY

 SURFICIAL DEPOSITS (from

 Carter and Redden, 1999b)

POTENTIOMETRIC CONTOUR—

 Shows altitude at which water

 would have stood in tightly cased,

 nonpumping wells (from Strobel

 and others, 2000b). Contour

 interval 100 feet. Dashed where

 inferred. Vertical datum is NGVD

 of 1929

FAULT—Dashed where approx-

 imated. Bar and ball on

 downthrown side

ANTICLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

SYNCLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

MONOCLINE—Showing trace

 of axial plane. Dashed

 where approximated

DOME—Symbol size approx-

 imately proportional to size

 of dome. Dome asymmetry

 indicated by arrow length

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
24 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 23. Potentiometric surface of the Inyan Kara aquifer.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Spring

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peakx

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

3,000

3,100

2,900

3,200

2,900

3,000

2,800

3,100 3,200

3,300

3,300

2,800

3,700

3,400

3,000

3,300

3,500

3,400

3,200

3,100

2,800

2,800

2,600

3,000

3,400 3,300

2,900

2,700

3,500

3,500 3,400

3,200

3,500

3,700

3,200

3,800

3,700

3,300

3,800

3,500

3,100

3,700

3,000

3,900

3,800

3,900

3,600

2,900

3,500

3,700

3,600

3,500

3,400

3,200

3,400

3,300

3,300

3,400 3,500

3,600

2,700

3,300

2,900 3,000

3,100

3,600

3,700

3,400

3,500

3,400

3,000

EXPLANATION

OUTCROP OF INYAN KARA

 GROUP

INYAN KARA GROUP ABSENT

INYAN KARA GROUP PRESENT,

 BUT OVERLAIN BY SURFICIAL

 DEPOSITS (from Carter and

 Redden, 1999a)

POTENTIOMETRIC CONTOUR—

 Shows altitude at which water

 would have stood in tightly cased,

 nonpumping wells (from Strobel

 and others, 2000a). Contour

 interval 100 feet, where

 appropriate. Dashed where

 inferred. Vertical datum is NGVD

 of 1929

FAULT—Dashed where approx-

 imated. Bar and ball on

 downthrown side

ANTICLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

SYNCLINE—Showing trace of

 axial plane and direction of

 plunge. Dashed where

 approximated

MONOCLINE—Showing trace

 of axial plane. Dashed

 where approximated

DOME—Symbol size approx-

 imately proportional to size

 of dome. Dome asymmetry

 indicated by arrow length

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Availability of Ground-Water Resources 25

Figure 24. Saturated thickness of the Madison aquifer.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

MADISON LIMESTONE ABSENT

OUTCROP OF MADISON

 LIMESTONE

Less than 200

SATURATED THICKNESS OF

 MADISON AQUIFER, IN

 FEET (from Clawges, 2000a)

200 to 400

400 to 600

600 to 800

Fully saturated

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
26 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 25. Saturated thickness of the Minnelusa aquifer.

N. Fork

Rapid

Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Rhoads Fork

Coolidge

Angostura

Reservoir

Castl e

Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELL

Creek

E

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall

R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver Cr

Whitetail

Cr

Cr

Cr

Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Highland

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Cre ek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Springs

Beaver Creek

Creek

Redbird

Cold

Canyon

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

T. 9 N.

T. 8 N.

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

T. 3 N.

T. 2 N.

T. 1 N.

T. 1 S.

T. 2 S.

T. 3 S.

T. 4 S.

T. 5 S.

T. 6 S.

T. 7 S.

T. 8 S.

T. 9 S.

T. 10 S.

R. 1 E. R. 2 E. R. 3 E. R. 4 E.

R. 5 E. R. 6 E. R. 7 E.

R. 8 E. R. 9 E.

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

EXPLANATION

MINNELUSA FORMATION ABSENT

OUTCROP OF MINNELUSA

 FORMATION

Less than 200

SATURATED THICKNESS OF

 MINNELUSA AQUIFER, IN

 FEET (from Clawges, 2000b)

200 to 400

400 to 600

600 to 800

800 to 1,000

1,000 to 1,200

Fully saturated

No data

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

0 10 20

0 10 20 MILES

KILOMETERS

Base modified from U.S. Geological Survey digital data, 1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996; Universal Transverse Mercator projection, zone 13
Water Quality of Ground-Water Resources 27

Figure 26. Selected hydrographs illustrating trends in ground-water levels.

C

3,450

3,600

3,500

3,550

Reptile Gardens Madison (site 4)

1984 1986 1988 1990 1992 1994 1996 1998

1984 1986 1988 1990 1992 1994 1996 1998

B

3,460

3,540

3,480

3,500

3,520

Redwater Minnelusa (site 3)

CALENDAR YEAR

1960 1965 1970 1975 1980 1985 1990 1995 1999

A Whitewood Madison (site 1)

Whitewood Minnelusa (site 2)

3,380

3,480

3,400

3,420

3,440

3,460

RAPID

CITY

LIMESTONE PLATEAU

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

104o 45' 103o30'

15' 103o

30'

44o45'

15'

44o

45'

30'

43o15'

1, 2

EXPLANATION

OUTCROP OF MADISON

 LIMESTONE

OUTCROP OF MINNELUSA

 FORMATION

4

3

WATER QUALITY OF GROUND-WATER 

RESOURCES

This section of the report includes a 

summary of water-quality characteristics for 

both major aquifers and selected minor aquifers in the Black Hills area. A summary of 

water quality relative to water use also is presented. More detailed descriptions of groundwater quality were presented by Williamson 

and Carter (2001). 

Water quality is a measure of the suitability of water for a particular use based on 

selected physical, chemical, and biological 

characteristics. The quality of ground water is 

an important consideration because aquifers 

provide water for a variety of purposes 

including drinking water, livestock watering, 

irrigation, and industrial use. The quality of 

water can change as it flows over the land surface in streams and lakes and as it flows 

underground. Because ground-water and surface-water resources in the Black Hills area 

can be highly interconnected, the quality of 

surface water can affect the quality of ground 

water, and vice versa.

Ground water can contain numerous 

substances (constituents) from natural and 

human sources that typically are measured 

using laboratory analyses. Some constituents 

potentially can cause serious health effects. 

As ground water comes in contact with soil 

and rock materials, some of the chemicals, 

minerals, and nutrients dissolve and become 

part of the water chemistry. Two fundamental 

factors influencing water chemistry are the 

type of geologic materials that are present 

and the length of time that water is in contact 

with those materials (Winter and others, 

1998), which typically increases constituent 

concentrations from natural sources.

Chemical constituents in ground water 

also can result from human sources, such as 

industrial, domestic, and agricultural chemicals, that have the potential to contaminate 

the water. The potential for ground-water 

contamination in the Black Hills area can be 

large because many of the outcrops, which 

are important aquifer recharge areas, could 

be subject to various forms of land development. Rapid ground-water velocities also are 

possible in many aquifers because of high 

secondary permeability. Contamination by 

septic tanks has been documented for some 

wells in the Blackhawk, Piedmont, and 

Sturgis areas (Bartlett and West Engineers, 

Inc., 1998).

Standards and guidelines have been 

established to protect water for various designated uses. The U.S. Environmental Protection Agency (USEPA) and the States are 

responsible for establishing the standards for 

constituents in water that have been shown to 

pose a risk to human health. Although 

drinking-water standards apply only to public 

water supplies, individuals using water from 

private wells should be aware of potential 

health risks associated with drinking water 

that exceeds these standards. Maximum Contaminant Levels (MCLs) are established for 

constituents that, if present in drinking water, 

may cause adverse human health effects; 

MCLs are enforceable health-based standards (U.S. Environmental Protection 

Agency, 1994). Secondary Maximum Contaminant Levels (SMCLs) are established for 

constituents that can adversely affect the 

taste, odor, or appearance of water and may 

result in discontinuation of use of the water; 

SMCLs are nonenforceable, generally nonhealth-based standards that are related to the 

aesthetics of water use (U.S. Environmental 

Protection Agency, 1994).

General Characteristics for Major 

Aquifers

A brief summary of water-quality characteristics from Williamson and Carter 

(2001) for the major aquifers in the study area 

(Deadwood, Madison, Minnelusa, Minnekahta, and Inyan Kara aquifers) is presented 

in this section of the report. Characteristics 

for the Precambrian aquifer also are included 

in this section of the report because numerous 

wells are completed in this aquifer in the 

crystalline core of the Black Hills.

Water temperature affects the usefulness of water for many purposes. For 

example, hot water needs to be cooled prior to 

consumption; however, hot water is desirable 

for geothermal heating purposes. The temperature of water from wells completed in the 

Madison aquifer is shown in figure 27. Water 

temperatures generally increase with well 

depth. Temperatures measured in the Madison aquifer generally are the warmest of the 

major aquifers in the study area because it 

generally is the deepest aquifer used at distance from the outcrop. The Madison aquifer 

is the primary source of water for warm 

artesian springs in the southern Black Hills; 

factors other than aquifer depth may affect 

water temperatures in this area (Whalen, 

1994).

The total of all dissolved mineral constituents is measured as the dissolved solids 

concentration. Specific conductance is a measure of the ability of water to conduct an electrical current. It is highly dependent on the 

amount of dissolved solids (such as salt) in 

the water. Pure water, such as distilled water, 

has a very low specific conductance. Specific 

conductance is an important water-quality 

measurement because it can be used to estimate dissolved solids concentrations, which 

may affect the taste of water and suitability 

for various uses. When comparing samples, a 

higher specific conductance indicates a 

higher dissolved solids concentration. Dissolved constituents tend to increase with residence time as indicated by the increase in 

specific conductance in the Madison and 

Minnelusa aquifers with distance from the 

Madison Limestone and Minnelusa Formation outcrops (figs. 28 and 29). 

Specific conductance generally is lower 

in water from the Precambrian, Deadwood, 

and Minnekahta aquifers than in water from 

the other major aquifers. Generally, water 

from the Inyan Kara aquifer is high in specific conductance even in some outcrop areas 

of the Inyan Kara Group (fig. 30) and is 

higher in specific conductance than the other 

major aquifers due to greater amounts of 

shale within the Inyan Kara Group. Water 

obtained from shales may contain rather high 

concentrations of dissolved solids (Hem, 

1985) and, hence, high specific conductance. 

Because depths to aquifers increase with distance from outcrop in most locations, concentrations of dissolved solids generally increase 

with well depth, as shown by the example 

relation in figure 31.
28 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 27. Water temperature in the Madison aquifer (modified from Williamson 

and Carter, 2001).

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

N. Fork Rapid Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Redbird Canyon

Cold

Beaver

Spring

C s

reek

Creek

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

Less than 20

WATER TEMPERATURE,

 IN DEGREES CELSIUS

20 to 30

30 to 40

40 to 50

Greater than 50

WELL COMPLETED IN MADISON

 AQUIFER FOR WHICH THERE

 IS A WATER TEMPERATURE

 MEASUREMENT

OUTCROP OF MADISON

 LIMESTONE

MADISON LIMESTONE

 ABSENT

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

Figure 28. Specific conductance in the Madison aquifer (modified from 

Williamson and Carter, 2001).

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

N. Fork Rapid Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Redbird Canyon

Cold

Beaver

Spring

C s

reek

Creek

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

OUTCROP OF MADISON

 LIMESTONE

MADISON LIMESTONE

 ABSENT

Less than 500

500 to 1,000

1,000 to 1,500

Greater than 1,500

SPECIFIC CONDUCTANCE

 OF SAMPLE, IN MICRO-

 SIEMENS PER CENTI-

 METER AT 25 DEGREES

 CELSIUS

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

Hardness is related to soap-consuming 

characteristics of water. Hard water can 

shorten the life of fabrics and may cause 

equipment damage. Hardness is determined 

primarily by the amount of dissolved calcium 

and magnesium in water. Water that has a 

hardness less than 61 mg/L (milligrams per 

liter) is considered soft; 61-120 mg/L, moderately hard; 121-180 mg/L, hard; and more 

than 180 mg/L, very hard (Heath, 1983). 

Geologic units that contain few carbonate 

rocks, such as the Precambrian-age rocks, 

generally contain water with lower hardness 

than geologic units that contain mostly carbonate rocks, which are composed primarily 

of calcium- and magnesium-bearing minerals. Water in the Madison, Minnelusa, and 

Minnekahta aquifers generally is hard to very 

hard (fig. 32) because the formations consist 

primarily of carbonate rocks. Water in the 

Deadwood aquifer also is hard to very hard 

because this unit consists primarily of sandstone with a calcium carbonate cement. 

Water in the Inyan Kara aquifer generally is 

hard to very hard in or near outcrop areas; 

however, hardness decreases with increasing 

distance from the outcrop (fig. 33). Similar to 

the other major bedrock aquifers, concentrations of dissolved solids in the Inyan Kara 

aquifer increase with increasing distance 

from the outcrop because calcium and bicarbonate are replaced by sodium and sulfate as 

water moves downgradient.

In the Black Hills area, water from the 

major aquifers generally is fresh and low in 

dissolved solids in and near outcrop areas 

except for parts of the Inyan Kara aquifer. 

The Madison, Minnelusa, and Inyan Kara 

aquifers may yield slightly saline water (dissolved solids concentrations between 1,000 

and 3,000 mg/L) at distance from the outcrops, especially in the southern Black Hills. 

The water in these aquifers is highly mineralized outside of the study area. In general, concentrations of sodium, chloride, and sulfate in 

the major aquifers increase with distance 

from the outcrop.

Sulfate affects the taste of water and has 

an SMCL of 250 mg/L. Sulfate concentrations in the Minnelusa aquifer are dependent 

on the amount of anhydrite present in the 

Minnelusa Formation. Near the outcrop, 

sulfate concentrations generally are low (less 

than 250 mg/L) because anhydrite has been 

removed by dissolution. An abrupt increase 

in sulfate concentrations occurs downgradient, where a transition zone occurs around 

the core of the Black Hills. This transition 

zone is an area within which the sulfate concentrations range from 250 to 1,000 mg/L 

(fig. 34) and marks an area of active removal 

of anhydrite by dissolution. Downgradient 

from the transition zone, sulfate concentrations are greater than 1,000 mg/L, which 

delineates a zone in which thick anhydrite 

beds remain in the formation. The transition 

zone probably is moving downgradient over 

geologic time as the anhydrite in the formation is dissolved (Kyllonen and Peter, 1987).
Water Quality of Ground-Water Resources 29

Figure 29. Specific conductance in the Minnelusa aquifer (modified from

Williamson and Carter, 2001).

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

N. Fork Rapid Cr

Belle Fourche Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Redbird Canyon

Cold

Beaver

Spring

Cree

s

k

Creek

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

OUTCROP OF MINNELUSA

 FORMATION

MINNELUSA FORMATION

 ABSENT

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

SPECIFIC CONDUCTANCE

 OF SAMPLE, IN MICRO-

 SIEMENS PER CENTI-

 METER AT 25 DEGREES

 CELSIUS

Less than 500

500 to 1,000

1,000 to 1,500

Greater than 1,500

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

Figure 30. Specific conductance in the Inyan Kara aquifer (modified from

Williamson and Carter, 2001).

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

N. Fork Rapid Cr

Belle Fourche Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Redbird Canyon

Cold

Beaver

Spring

C s

reek

Creek

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT

SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

OUTCROP OF INYAN KARA

 GROUP

INYAN KARA GROUP

 ABSENT

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

SPECIFIC CONDUCTANCE

 OF SAMPLE, IN MICRO-

 SIEMENS PER CENTI-

 METER AT 25 DEGREES

 CELCIUS

Less than 500

500 to 1,000

1,000 to 1,500

Greater than 1,500

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

Radionuclides are unstable isotopes 

that exist throughout the environment and 

have a certain probability of decay. Because 

several radionuclides are known to cause 

various types of cancer, drinking-water standards exist for these radionuclides. Most naturally occurring radionuclides in water are 

the result of radioactive decay of uranium and 

thorium. Radioactivity is the release of 

energy and energetic particles by changes 

occurring within atomic or nuclear structures 

(Hem, 1985). Alpha, beta, and gamma radiation are types of radiation that commonly are 

measured in ground water. Radionuclide 

analyses can be expressed in terms of disintegrations per unit time (typically in units of 

picocuries per liter) or in mass units (typically in units of micrograms per liter). Some 

of the radionuclide names include numbers, 

such as radium-226 and radium-228; these 

numbers represent chemical variations of the 

element.

Radium locates primarily in bone in 

humans; however, inhalation or ingestion of 

radium may result in lung cancer. Inhaled 

radon is known to cause lung cancer, and 

ingested radon is believed to cause cancer. In 

the Deadwood aquifer, more than 30 percent 

of the samples analyzed for radium-226 or 

radium-226 and radium-228 exceeded the 

MCL of 5 pCi/L (picocuries per liter) for the 

combined radium-226 and radium-228 standard. Almost 90 percent of the samples from 

the Deadwood aquifer exceed the proposed 

MCL of 300 pCi/L for radon in States 

without an active indoor air program (U.S. 

Environmental Protection Agency, 1999); 

three of these samples also exceed the proposed MCL of 4,000 pCi/L for radon in 

States with an active indoor air program (U.S. 

Environmental Protection Agency, 1999) 

(fig. 35). 

Uranium is a chemical and radiological 

hazard and carcinogen. Uranium deposits 

have been discovered and mined in the Inyan 

Kara Group in the southern Black Hills. Uranium may be introduced into the Inyan Kara 

Group by the artesian recharge of water from 

the Minnelusa aquifer (Gott, 1974). Some 

water in the Inyan Kara aquifer, especially in 

the southern Black Hills, contains relatively 

high concentrations of radionuclides. Almost 

20 percent of the samples collected from the 

Inyan Kara aquifer exceed the MCL for the 

combined radium-226 and radium-228 standard; all but one of the samples exceeding 

this standard were from wells in the southern 

Black Hills. About 4 percent of the samples 

from the Inyan Kara aquifer exceed the MCL 

of 30 μg/L (micrograms per liter) for uranium; all the samples exceeding the uranium 

MCL were from wells located in the southern 

Black Hills. In general, gross alpha-particle 

activity, gross-beta activity, and radium-226 

are higher in the Deadwood and Inyan Kara 

aquifers than in the Madison, Minnelusa, and 

Minnekahta aquifers. 
30 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 31. Relation between dissolved solids and well depth for Madison aquifer.

WELL DEPTH, IN FEET

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

100

10,000

150

200

250

300

400

500

600

700

800

900

1,000

1,500

2,000

2,500

3,000

4,000

5,000

6,000

7,000

8,000

9,000

DISSOLVED SOLIDS, SUM OF CONSTITUENTS,

IN MILLIGRAMS PER LITER

R2 = 0.4812

General Characteristics for Minor 

Aquifers

A brief summary of water-quality characteristics from Williamson and Carter 

(2001) for minor aquifers in the study area is 

presented in this section of the report. The 

minor aquifers in the study area include the 

Newcastle aquifer, alluvial aquifers, and local 

aquifers that exist in various semiconfining 

and confining units. These local aquifers 

include the Spearfish, Sundance, Morrison, 

Graneros, and Pierre aquifers.

Water in many of the minor aquifers can 

be very hard (fig. 32) and high in dissolved 

solids concentrations. Most samples from the 

Sundance aquifer indicate slightly saline 

water. Sulfate concentrations also can be high 

in the minor aquifers, such as the Spearfish 

aquifer where high sulfate concentrations can 

result from dissolution of gypsum. Both dissolved solids and sulfate concentrations are 

low in the Newcastle aquifer. In general, the 

dominance of sodium and sulfate increases 

with increasing amounts of shale present in 

the geologic units. The dominance of calcium, magnesium, and bicarbonate increases 

with increasing amounts of sandstone and 

carbonate rocks present in the geologic units. 

Concentrations of dissolved solids in 

alluvial aquifers generally increase with 

increasing distance from the core of the Black 

Hills, which is largely due to contact with 

underlying geologic units and alluvial materials derived from underlying units. Wells 

completed in alluvial deposits that do not 

overlie Cretaceous-age shales generally yield 

fresh water. Wells that are completed in alluvial deposits that overlie the Cretaceous-age 

shales generally yield slightly saline water in 

which sodium and/or sulfate is dominant. 

Samples from alluvial aquifers may be high 

in uranium concentrations, especially in the 

southern Black Hills. 

Ground-Water Quality Relative to 

Water Use

Concentrations exceeding SMCLs and 

MCLs affect the use of water in some areas 

for many aquifers within the study area. Most 

concentrations exceeding standards are for 

various SMCLs and generally affect the water 

only aesthetically. Radionuclide concentrations can be high in some of the major aquifers, especially in the Deadwood and Inyan 

Kara aquifers, and may preclude the use of 

water in some areas. Hard water may require 

special treatment for certain uses. Other factors, such as high concentrations of sodium 

and dissolved solids, may affect irrigation 

use. Water from all aquifers, with the exceptions of the Pierre and Sundance aquifers, 

generally is suitable for irrigation in most 

locations.

High concentrations of iron and manganese, which can stain, occasionally can 

hamper the use of water from the Precambrian aquifer. None of the reported samples 

from the Precambrian aquifer exceeded 

drinking-water standards for radionuclides.

Figure 32. Boxplots showing hardness for selected aquifers (from Williamson and Carter, 2001).

25th percentile

Median

75th percentile

Data value less than or equal to 1.5 times the interquartile

range outside the quartile

Outlier data value less than or equal to 3 and more than 1.5

times the interquartile range outside the quartile

Outlier data value more than 3 times the interquartile range

outside the quartile

EXPLANATION

15 Number of samples

AQUIFER

Precambrian

Deadwood

Madison

Minnelusa

Minnekahta

Inyan KaraSpearfishSundance

Morrison

Pierre

Graneros Alluvial

Newcastle

0

3,000

500

1,000

1,500

2,000

2,500

HARDNESS, IN MILLIGRAMS PER LITER

112 37 127 249 28 176 13 14 15 28 10 8 116
Water Quality of Ground-Water Resources 31

Figure 33. Hardness in the Inyan Kara aquifer (modified from Williamson and 

Carter, 2001).

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

N. Fork Rapid Cr

Belle Fourche Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Redbird Canyon

Cold

Beaver

Spring

C s

reek

Creek

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

0 10 20

0 10 20 MILES

KILOMETERS

EXPLANATION

Very hard, greater than 180

WATER HARDNESS, IN MILLI-

 GRAMS PER LITER

Hard, 121 to 180

Moderately hard, 61 to 121

Soft, less than 61

WELL COMPLETED IN INYAN

 KARA AQUIFER FOR

 WHICH THERE IS A HARD-

 NESS ANALYSIS

OUTCROP OF INYAN KARA

 GROUP

INYAN KARA GROUP ABSENT

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

Figure 34. Sulfate concentrations in the Minnelusa aquifer (modified from 

Naus and others, 2001).

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

N. Fork Rapid Cr

Belle Fourche Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Redbird Canyon

Cold

Beaver

Spring

C s

reek

Creek

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne

Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

0 10 20

0 10 20 MILES

KILOMETERS

Less than 250

SULFATE CONCENTRATION,

 IN MILLIGRAMS PER

 LITER

250 to 1,000

Greater than 1,000

WELL COMPLETED IN

 MINNELUSA AQUIFER

 FOR WHICH THERE IS

 A SULFATE ANALYSIS

EXPLANATION

OUTCROP OF MINNELUSA

 FORMATION

MINNELUSA FORMATION

 ABSENT

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

The principal deterrents to use of water 

from the Deadwood aquifer are high concentrations of radionuclides, including radium226 and radon. In addition, concentrations of 

iron and manganese can be high.

Water from the Madison aquifer can 

contain high concentrations of iron and manganese that may hamper its use. Water from 

the Madison aquifer is hard to very hard and 

may require special treatment for certain 

uses. In downgradient wells (generally 

deeper than 2,000 feet), concentrations of 

dissolved solids and sulfate also may deter 

use from this aquifer. Hot water, from deep 

wells and in the Hot Springs area, may not be 

desirable for some uses. Radionuclide concentrations in the Madison aquifer generally 

are acceptable.

In water from the Minnelusa aquifer, 

hardness and high concentrations of iron and 

manganese may hamper use. Generally, 

downgradient wells (generally deeper than 

1,000 feet) also have high concentrations of 

dissolved solids and sulfate. Hot water from 

deep wells may not be desirable for some 

uses. Arsenic concentrations in the Minnelusa aquifer exceed the MCL of 10 μg/L in 

some locations. Only a few samples exceed 

the MCLs for various radionuclides.

The use of water from the Inyan Kara 

aquifer may be hampered by high concentrations of dissolved solids, iron, sulfate, and 

manganese. In the southern Black Hills, 

radium-226 and uranium concentrations in 

water from this aquifer also may preclude its 

use. Hard water from wells located on or near 

the outcrop of the Inyan Kara Group may 

require special treatment. Suitability for irrigation may be affected by high dissolved 

solids and sodium concentrations.

The use of water from the minor aquifers may be hampered by hardness and concentrations of dissolved solids and sulfate. 

Concentrations of radionuclides, with the 

exception of uranium, generally are at acceptable levels in samples from these minor 

aquifers. Concentrations of selenium, which 

may be harmful or potentially toxic if 

ingested in moderate excess for a long time 

(Callahan and others, 1979), are an additional 

deterrent to use of water from the Sundance 

aquifer in some places. Water from the Pierre 

and Sundance aquifers generally is not suitable for irrigation because dissolved solids 

concentrations generally are high. Water 

from the other minor aquifers generally is 

suitable for irrigation, but may not be in specific locations if concentrations of either 

dissolved solids or sodium are high.

Water from alluvial aquifers generally 

is very hard and may require special treatment for certain uses. High concentrations of 

dissolved solids, sulfate, iron, and manganese 

may limit the use of water from alluvial aquifers that overlie the Cretaceous-age shales. In 

the southern Black Hills, uranium concentrations in alluvial aquifers can be high in many 

locations.
32 Ground-Water Resources in the Black Hills Area, South Dakota

Figure 35. Radon concentrations in the Deadwood aquifer (modified from Williamson and Carter, 2001).

BUTTE CO

LAWRENCE CO MEADE CO

PENNINGTON CO

CUSTER CO

FALL RIVER CO

WYOMING

SOUTH DAKOTA

N. Fork Rapid Cr

Belle Fourche

Reservoir

FOURCHE

Victoria

Spring

Rhoads Fork

Coolidge

Highland

Angostura

Reservoir

Castl e Cr

N. Fork Castle Cr

Hell

Canyon

Canyon

Red

Bear

Gulch

Creek

Crow

Sheridan

Lake

Hot Brook Canyon

Cox

Lake

Deerfield

Reservoir

Pactola

Reservoir

Indian Cr

Horse

Creek

Owl

BELLE

Creek

RIVER

REDWATER

R I VER

Creek

Cr

Little Spearfish

Spearfish

Creek

Spearfish

Whitewood

Creek

Creek

Bear

Butte

Elk

Elk

Creek

Creek

Creek

Boxelder

Rapid

Rapid

Creek

Creek

Creek

Spring

Creek

French

Creek

Creek

Creek

Grace

Creek

Creek

Creek

S. Fork

Gillette

S. Fork Rapid Cr

Battle

French

Beaver

Beaver

Creek

Creek

Creek

Creek

Creek

Creek

Fall R

Hat

Creek

Creek

Horsehead

CHEYENNE

RIVER

Cottonwood

Hay Creek

Bottom

False

Creek

Spokane

Lame

Johnny

Higgins

Beaver

Cr

Whitetail

Cr

Cr

Cr Cr

Gulch

Annie

Squaw

Deadwood

Iron Cr

Cottonwood

Creek

Alkali

Iron Cr

Elk

Little

Creek

Castle

Castle

Creek

Creek

Bear Gulch

Sylvan

Lake

Cold B roo k

Cr Strawberry

Boles

Canyon

Canyon

Redbird Canyon

Cold

Beaver

Spring

C s

reek

Creek

Whitewood

Spearfish

Saint

Onge

DEADWOOD

Lead

BELLE FOURCHE

Newell

STURGIS

Blackhawk

Piedmont

Tilford

Box Elder 

Hill City

Hermosa

CUSTER

HOT SPRINGS

Edgemont

Minnekahta

Tinton

Cheyenne Crossing

Central

City

Roubaix

Nemo

Vale

Nisland

Hayward

Keystone

Rochford

Pringle

Fairburn

Buffalo Gap

Dewey

Cascade

Springs

Igloo

Provo

Oral

Rockerville

RAPID CITY

LIMESTONE PLATEAU

 Wind Cave

National Park

Jewel Cave

National

Monument

Mt. Rushmore

National

Memorial

CUSTER

STATE

PARK

Wind

Cave

Harney

Peak

x

Calamity

Peak

x

Iron

Mountain x

Onyx

Cave

Bear

x Butte

Ellsworth

Air Force

Base

5,800

6,600

5,300

2,700

1,400

1,500

900

560

920 800

1,600

220

80

1,300

690

5,800

6,600

5,300

2,700

1,400 1,100

1,500

900

560

920 800

1,600

220

80

1,300

690

0 10 20

0 10 20 MILES

KILOMETERS

OUTCROP OF DEADWOOD

 FORMATION

DEADWOOD FORMATION

 ABSENT

RADON CONCENTRATION

 OF SAMPLE—Number is

 radon concentration in

 picocuries per liter 

Less than 300

300 to 3,000

Greater than 3,000

EXPLANATION

80

500

5,300

104o 45' 103o

30'

15' 103o

30'

44o

45'

15'

44o

45'

30'

43o

15'

Base modified from U.S. Geological Survey digital data,

1:100,000, 1977, 1979, 1981, 1983, 1985

Rapid City, Office of City Engineer map, 1:18,000, 1996

Universal Transverse Mercator projection, zone 13

SUMMARY

The availability of ground-water 

resources in the Black Hills area is influenced 

by many factors including location, local 

recharge and ground-water flow conditions, 

and structural features. Thus, the availability 

of water is variable throughout the Black 

Hills area, and even when water is available, 

it may not be suitable for various uses 

depending on the water quality. 

The major bedrock aquifers in the 

Black Hills area are the Deadwood, Madison, 

Minnelusa, Minnekahta, and Inyan Kara 

aquifers. Minor bedrock aquifers occur in 

other hydrogeologic units, including confining units, due to fracturing and interbedded permeable layers. 

The Precambrian-age basement rocks 

generally have low permeability and form the 

lower confining unit for a series of sedimentary aquifers. However, localized aquifers 

occur in the igneous and metamorphic rocks 

that make up the central crystalline core of 

the Black Hills and are referred to collectively as the Precambrian aquifer. Water-table 

(unconfined) conditions generally occur in 

the Precambrian aquifer, and topography can 

strongly control ground-water flow directions. The aquifer is considered to be contained in the area where the Precambrian-age 

rocks are exposed in the central core of the 

Black Hills. 

Surrounding the central crystalline core 

is a layered series of sedimentary rocks 

including limestones, sandstones, and shales 

that are exposed in roughly concentric rings 

around the uplifted flanks of the Black Hills. 

The more permeable of these sedimentary 

rocks—the Deadwood Formation, Madison 

Limestone, Minnelusa Formation, Minnekahta Limestone, and Inyan Kara Group—

contain major aquifers that are able to store 

and transmit large quantities of water and are 

used extensively as water supplies within and 

beyond the study area. Alluvial deposits 

along streams also commonly are used as 

local aquifers.

Various information and maps are presented in this report to help characterize 

water availability and quality in locations 

throughout the Black Hills. However, there is 

no guarantee of obtaining usable water at any 

location due to the extreme potential variability in conditions that can affect the availability and quality of ground water in the 

area. Maps presented in this report include 

the distribution of hydrogeologic units; depth 

to the top of the five formations that contain 

major aquifers; thickness of the five formations that contain major aquifers; potentiometric maps for the five major aquifers; 

saturated thickness of the Madison and 

Minnelusa aquifers; water temperature in the 

Madison aquifer; specific conductance in the 

Madison, Minnelusa, and Inyan Kara aquifers; hardness in the Inyan Kara aquifer; sulfate concentrations in the Minnelusa aquifer; 

and radon concentrations in the Deadwood 

aquifer. 

The total volume of recoverable water 

stored in the major aquifers (including the 

Precambrian aquifer) within the study area is 

estimated as 256 million acre-feet. Although 

the volume of stored water is very large, 

water quality may not be suitable for all uses 

in some parts of the study area.

Water-level records are presented for 

selected observation wells to illustrate potential fluctuations in water levels that can occur 

in the bedrock aquifers. In general, there is 

very little indication of long-term water-level 

declines from ground-water withdrawals in 

any of the bedrock aquifers in the Black Hills 

area. However, dry wells or reduced pumping 

capacity could result during periods of 

declining water levels.

Most limitations for the use of ground 

water are related to aesthetic qualities associated with hardness and high concentrations of 

chloride, sulfate, sodium, manganese, and 

iron. Water from the major bedrock aquifers 

generally is fresh and low in dissolved solids 

concentrations in and near outcrop areas but 

becomes progressively more saline with distance from the outcrops. In the Minnelusa 

aquifer, concentrations of dissolved sulfate 

vary markedly over short distances, influenced by a zone of active anhydrite dissolution. Water from most minor aquifers 

generally has higher concentrations of dissolved sulfate than major aquifers because of 

larger influence from shale layers.

Water from all aquifers, with the exceptions of the Pierre and Sundance aquifers, 

generally is suitable for irrigation in most 

locations. Very few health-related limitations 

exist for ground water; most of these limitations are for radionuclides, such as radon and 

uranium, especially in the Deadwood and 

Inyan Kara aquifers. In addition, high concentrations of arsenic have been detected in a 

few samples from the Minnelusa aquifer.
References 33

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environmental fate of 129 priority pollutants, 

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Lindquist, V.A., 2002, Atlas of water 

resources in the Black Hills area, South 

Dakota: U.S. Geological Survey Hydrologic 

Investigations Atlas HA-747, 120 p.

Carter, J.M., and Redden, J.A., 1999a, Altitude of 

the top of the Inyan Kara Group in the Black 

Hills area, South Dakota: U.S. Geological 

Survey Hydrologic Investigations Atlas HA744-A, 2 sheets, scale 1:100,000.

———1999b, Altitude of the top of the Minnekahta Limestone in the Black Hills area, 

South Dakota: U.S. Geological Survey 

Hydrologic Investigations Atlas HA-744-B, 

2 sheets, scale 1:100,000.

———1999c, Altitude of the top of the Minnelusa Formation in the Black Hills area, 

South Dakota: U.S. Geological Survey 

Hydrologic Investigations Atlas HA-744-C, 

2 sheets, scale 1:100,000.

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Limestone in the Black Hills area, South 

Dakota: U.S. Geological Survey Hydrologic 

Investigations Atlas HA-744-D, 2 sheets, 

scale 1:100,000.

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Clark, D.W., and Briar, D.W., 1993, What is 

ground water?: U.S. Geological Survey 

Open-File Report 93-643, 2 p.

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thickness of the Madison aquifer, Black 

Hills, South Dakota: U.S. Geological Survey 

data available on the World Wide Web, 

accessed July 2, 2001, at URL 

http://water.usgs.gov/lookup/

getspatial?sd_mdsnst_thk

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of the Minnelusa aquifer, Black Hills, South 

Dakota: U.S. Geological Survey data available on the World Wide Web, accessed 

July 2, 2001, at URL http://water.usgs.gov/

lookup/getspatial?sd_mnlsst_thk

DeWitt, Ed, Redden, J.A., Wilson, A.B., and 

Buscher, David, 1986, Mineral resource 

potential and geology of the Black Hills 

National Forest, South Dakota and 

Wyoming: U.S. Geological Survey Bulletin 

1580, 135 p. 

Driscoll, D.G., Bradford, W.L., and Moran, M.J., 

2000, Selected hydrologic data, through 

water year 1998, Black Hills Hydrology 

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Survey Open-File Report 00-70, 284 p.

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Putnam, L.D., 2002, Hydrology of the Black 

Hills area, South Dakota: U.S. Geological 

Survey Water-Resources Investigations 

Report 02-4094, 150 p.

Driscoll, D.G., Hamade, G.R., and Kenner, S.J., 

2000, Summary of precipitation data for the 

Black Hills area of South Dakota, water 

years 1931-98: U.S. Geological Survey 

Open-File Report 00-329, 151 p.

Epstein, J.B., 2000, Gypsum karst and hydrologic 

evolution in the northern Black Hills, South 

Dakota, in Strobel, M.L., and others, eds., 

Hydrology of the Black Hills—Proceedings 

of the 1999 Conference on the Hydrology of 

the Black Hills: Rapid City, S. Dak., South 

Dakota School of Mines and Technology 

Bulletin No. 20, p. 73-79.

Galloway, JM., 2000, Digital map of generalized 

thickness of the Madison Limestone and 

Englewood Formation, Black Hills, South 

Dakota: U.S. Geological Survey data available on the World Wide Web, accessed 

July 2, 2001, at URL http://water.usgs.gov/

lookup/getspatial?sd_mdsn_thk

Gott, G.B., Wolcott, D.E., and Bowles, C.G., 

1974, Stratigraphy of the Inyan Kara Group 

and localization of uranium deposits, southern Black Hills, South Dakota and Wyoming: 

U.S. Geological Survey Professional Paper 

763, 57 p.

Greene, E.A., 1993, Hydraulic properties of the 

Madison aquifer system in the western Rapid 

City area, South Dakota: U.S. Geological 

Survey Water-Resources Investigations 

Report 93-4008, 56 p.

Gries, J.P., 1996, Roadside geology of South 

Dakota: Missoula, Mont., Mountain Press 

Publishing Company, 358 p.

Heath, R.C., 1983, Basic ground-water hydrology: U.S. Geological Survey Water-Supply 

Paper 2220, 84 p.

Hem, J.D., 1985, Study and interpretation of 

chemical characteristics of natural water (3d 

ed.): U.S. Geological Survey Water-Supply 

Paper 2254, 263 p.

Jarrell, G.J., 2000a, Digital map of depth to the 

top of the Deadwood Formation: U.S. 

Geological Survey data available on the 

World Wide Web, accessed July 2, 2001, at 

URL http://water.usgs.gov/lookup/ 

getspatial?sd_ddwd_dep

———2000b, Digital map of depth to the top of 

the Madison Limestone: U.S. Geological 

Survey data available on the World Wide 

Web, accessed July 2, 2001, at URL 

http://water.usgs.gov/lookup/ 

getspatial?sd_mdsn_dep

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the Minnelusa Formation: U.S. Geological 

Survey data available on the World Wide 

Web, accessed July 2, 2001, at URL 

http://water.usgs.gov/lookup/ 

getspatial?sd_mnls_dep

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the Minnekahta Limestone: U.S. Geological 

Survey data available on the World Wide 

Web, accessed July 2, 2001, at URL 

http://water.usgs.gov/lookup/ 

getspatial?sd_mnkt_dep

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the Inyan Kara Group: U.S. Geological Survey data available on the World Wide Web, 

accessed July 2, 2001, at URL 

http://water.usgs.gov/lookup/ 

getspatial?sd_inkr_dep

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Hills, South Dakota: U.S. Geological Survey 

data available on the World Wide Web, 

accessed July 2, 2001, at URL 

http://water.usgs.gov/lookup/ 

getspatial?sd_mnls_thk

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Minnelusa, and Madison aquifers of the 

northern Black Hills, South Dakota and 

Wyoming, and Bear Lodge Mountains, 

Wyoming: U.S. Geological Survey WaterResources Investigations Report 86-4158, 

61 p.

Long, A.J., 2000, Modeling techniques for karst 

aquifers—Anisotropy, dual porosity, and linear systems analysis: Rapid City, S. Dak., 

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analysis of the Madison and Minnelusa aquifers in the Rapid City area, South Dakota—

Conceptual model: U.S. Geological Survey 

Water-Resources Investigations Report 02-

4185, 100 p.

Long, A.J., Strobel, M.L., and Hamade, G.H., 

1999, Localized leakage between the Madison and Minnelusa aquifers in the eastern 

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Geological Society of America Abstracts 

with Programs, October 25-28, 1999, p. 412.

Naus, C.A., Driscoll, D.G., and Carter, J.M., 

2001, Geochemistry of the Madison and 

Minnelusa aquifers in the Black Hills area, 

South Dakota: U.S. Geological Survey 

Water-Resources Investigations Report 

01-4129, 118 p.

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water from the bedrock aquifers in the Rapid 

City area, South Dakota: U.S. Geological 

Survey Water-Resources Investigations 

Report 85-4022, 34 p.

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rocks of western South Dakota, in Rich, F.J., 

ed., Geology of the Black Hills, South 

Dakota and Wyoming (2d ed.): Geological 

Society of America, Field Trip Guidebook, 

American Geological Institute, p. 154-174.

Strobel, M.L., Galloway, J.M., Hamade, G.R., 

and Jarrell, G.J., 2000a, Potentiometric surface of the Inyan Kara aquifer in the Black 

Hills area, South Dakota: U.S. Geological 

Survey Hydrologic Investigations Atlas HA745-A, 2 sheets, scale 1:100,000.

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Minnekahta aquifer in the Black Hills area, 

South Dakota: U.S. Geological Survey 

Hydrologic Investigations Atlas HA-745-B, 

2 sheets, scale 1:100,000.

———2000c, Potentiometric surface of the 

Minnelusa aquifer in the Black Hills area, 

South Dakota: U.S. Geological Survey 

Hydrologic Investigations Atlas HA-745-C, 

2 sheets, scale 1:100,000.

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Madison aquifer in the Black Hills area, 

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Hydrologic Investigations Atlas HA-745-D, 

2 sheets, scale 1:100,000.

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Deadwood aquifer in the Black Hills area, 

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2 sheets, scale 1:100,000.

Strobel, M.L., Jarrell, G.J., Sawyer, J.F., Schleicher, J.R., and Fahrenbach, M.D., 1999, Distribution of hydrogeologic units in the Black 

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the artesian basin of the Dakotas: Geological 

Society of America Bulletin 1081-B, p. 163-

182. 
34 Ground-Water Resources in the Black Hills Area, South Dakota

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Summary of EPA finalized National primary 

drinking water regulations: U.S. Environmental Protection Agency Region VIII, 

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rule: U.S. Environmental Protection 

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6 p.

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cycle: U.S. Geological Survey General Interest Publication [pamphlet].

Whalen, P.J., 1994, Source aquifers for Cascade 

Springs, Hot Springs, and Beaver Creek 

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Dakota: Rapid City, S. Dak., South Dakota 

School of Mines and Technology, unpublished M.S. thesis, 299 p.

Williamson, J.E., and Carter, J.M., 2001, Waterquality characteristics in the Black Hills area, 

South Dakota: U.S. Geological Survey 

Water-Resources Investigations Report 01-

4194, 196 p.

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Alley, W.M., 1998, Ground water and surface water—A single resource: U.S. Geological Survey Circular 1139, 79 p.
Glossary 35

GLOSSARY

Alluvium A general term for unconsolidated sedimentary accumulations 

deposited by rivers or streams. It includes sediment deposited in river beds 

and flood plains.

Anhydrite A calcium sulfate mineral (CaSO4) that alters readily to gypsum.

Anticline A fold in which the strata dip away from the axis. After erosion, 

the oldest rocks are exposed in the central core of the fold.

Aquifer An underground body of porous materials, such as sand, gravel, or 

fractured rock, filled with water and capable of supplying useful quantities 

of water to a well or spring.

Artesian aquifer An aquifer that contains water that would rise above the 

top of the aquifer in a penetrating well; also confined aquifer.

Artesian well A well in which the water will rise above the top of the 

aquifer. When the water level is above land surface, water will flow from the 

well.

Axial plane With reference to folds, such as anticlines and synclines, an 

imaginary plane that intersects the crest or trough of a fold. 

Basal Located at the bottom of a geologic unit.

Bedrock aquifer An aquifer composed of consolidated material such as 

limestone, dolomite, sandstone, siltstone, shale, or fractured crystalline rock.

Carbonate rocks Rocks consisting mainly of carbonate minerals, which 

contain the carbonate radical (CO3

-2) combined with other elements. Examples are limestone and dolomite.

Cenozoic The most recent of the four eras into which geologic time is 

divided. It extends from the end of the Mesozoic Era to the present.

Clay An earthy, extremely fine-grained sediment or soft rock composed 

primarily of clay-sized or colloidal particles, having high plasticity and a 

considerable content of clay minerals.

Colluvium A general term applied to unconsolidated material deposited by 

rainwash or slow continuous downslope creep, usually collecting at the base 

of hillsides.

Concentration The amount of a constituent present in a given volume of 

sample. Usually expressed as milligrams per liter or micrograms per liter for 

a water sample.

Confined Said of ground water that is under pressure greater than that of the 

atmosphere. When an aquifer is completely filled with water (fully saturated) 

and is overlain by a confining unit, the water can be confined under pressure.

Confined aquifer An aquifer that contains water that would rise above the 

top of the aquifer in a penetrating well; also artesian aquifer. See figure 1B.

Confining unit A relatively low permeability geologic unit that impedes the 

vertical movement of water. 

Conglomerate A coarse-grained sedimentary rock composed of rounded 

fragments of pebbles, cobbles, or boulders cemented into a solid mass.

Constituent A chemical substance in water that can be measured by analytical methods.

Cross section A diagram or drawing that shows features transected by a 

given vertical plane. See figure 6.

Crystalline rock Igneous or metamorphic rock.

Dip The slope of a tilted layer of rock.

Dissolution Process by which minerals and rock materials are dissolved by 

a fluid.

Dissolved solids The total of all dissolved mineral constituents, usually 

expressed in milligrams per liter (mg/L). The dissolved solids concentration 

commonly is called the water’s salinity and is classified as follows: fresh, 

0-1,000 mg/L; slightly saline, 1,000-3,000 mg/L; moderately saline, 3,000-

10,000 mg/L; very saline, 10,000-35,000 mg/L; and briny, more than 35,000 

mg/L.

Dolomite A sedimentary rock composed primarily of calcium-magnesium 

carbonate, CaMg(CO3)2.

Dome An uplift that is circular or elliptical in map view, with beds dipping 

away in all directions from a central area. 

Effective porosity The porosity consisting of interconnected voids.

Fault A surface along which a rock body has broken and been displaced. 

Fold A bend or flexure in a rock. 

Formation The fundamental unit in the local classification of rocks into 

geologic units based on similar characteristics in lithology, which is the 

description of rocks on the basis of such characteristics as color, mineralogic 

composition, and grain size. Formations may represent rocks deposited during short or long time intervals, may be composed of materials from several 

sources, and may include breaks in deposition. Formations typically are 

named after geographic localities where they were first studied or described.

Fracture A crack in a rock. Also includes joints and faults.

Fresh water Water that has a dissolved solids concentrations of less than 

1,000 milligrams per liter.

Geologic time scale An arbitrary chronologic arrangement of geologic 

events, commonly presented in a chart form with the oldest event and time 

unit at the bottom and the youngest at the top.

Ground water Water beneath the land surface in the saturated zone.

Ground-water level The level of the water table in an unconfined aquifer 

or of the potentiometric surface in a confined aquifer.

Group A geologic classification consisting of two or more formations.

Gypsum The mineral form of hydrated calcium sulfate, CaSO4

2

2H2O.

Hogback A steep, elongate ridge; commonly protected from erosion by a 

steeply dipping resistant stratum.

Hydraulic connection Exists when changes in hydraulic head in adjacent 

aquifers or surface-water bodies influence each other.

Hydraulic gradient The rate of change in total head per unit of distance of 

flow in a given direction. Water will flow from higher hydraulic head to 

lower hydraulic head.

Hydraulic head In an aquifer, the altitude to which water will rise in a properly constructed well. This is the altitude of the water table in an unconfined 

aquifer or of the potentiometric surface in a confined aquifer.

Hydrogeology Factors that deal with geologic influences on water.

Hydrograph A graph showing flow rates or water levels with respect to 

time. A stream hydrograph commonly shows rate of flow; a well hydrograph 

commonly shows water level.

Igneous rocks Rocks that solidified from molten or partly molten material, 

such as magma. Granite is an example of an igneous rock.

Infiltration Movement of water from the land surface into the soil or porous 

rock.

Intrusion The process of emplacement of magma in pre-existing rock.

Isotope One of two or more species of the same chemical element that differ from one another by having a different number of neutrons in the nucleus. 

The isotopes of an element have slightly different physical and chemical 

properties due to their mass difference.

Karst A type of topography that is formed over limestone, dolomite, or 

gypsum by dissolution. It is characterized by sinkholes, caves, and underground drainage.

Laminated Said of a rock containing very thin layers; platy.

Limestone A sedimentary rock consisting mostly of calcium carbonate, 

CaCO3, primarily in the form of the mineral calcite.

Massive Said of rocks that occur in very thick beds that are uniform in 

structure and composition throughout.

Maximum Contaminant Level (MCL) Maximum permissible level of a contaminant in water that is delivered to any user of a public water system. 

MCL’s are enforceable standards established by the U.S. Environmental 

Protection Agency.

Mean The arithmetic average of a series of values.

Median The value of the middle number in a set of data arranged in rank 

order. The 50th percentile.

Mesozoic The era of geologic time from the end of the Paleozoic Era to the 

beginning of the Cenozoic Era.

Metamorphic rock Derived from pre-existing rocks in response to changes 

to temperature, pressure, or stress that result in changes in the mineralogy, 

chemistry, or structure of the rock. Examples of metamorphic rocks are slate 

and schist.

Monocline A step-like bend or fold in otherwise horizontal or gently 

dipping beds. 

Nutrients Nitrogen and phosphorus, which are essential to plant growth.
36 Ground-Water Resources in the Black Hills Area, South Dakota

Observation well A well constructed for collection of hydrologic data, 

such as water levels and water quality.

Outcrop That part of a geologic formation that is exposed at the land 

surface.

Paleozoic The era of geologic time from the end of the Precambrian Era to 

the beginning of the Mesozoic Era.

Perched ground water Unconfined ground water separated from an underlying main body of ground water by an unsaturated zone.

Permeability The capacity of a porous rock, sediment, or soil for transmitting a fluid.

Porosity The percentage of the soil or rock volume that is occupied by pore 

space, void of material; defined by the ratio of voids to the total volume of a 

specimen.

Potentiometric surface A surface representing the hydraulic head of 

ground water; represented by the water-table altitude in an unconfined aquifer or by the altitude to which water will rise in a properly constructed well 

in a confined aquifer.

Precambrian The oldest geologic time period, which occurred before the 

beginning of the Paleozoic Era. The Precambrian Era constitutes about 

90 percent of all geologic time.

Public water supply Water supply provided to the public; defined in South 

Dakota as having at least 15 service connections or regularly serving at least 

25 individuals daily for at least 60 days out of the year.

Radioactive decay Spontaneous emission of particles (alpha or beta) and 

gamma rays from the nucleus of an unstable nuclide. The resulting product 

nucleus may be stable or unstable, in which case decay continues until a 

stable nuclide is formed.

Radioactivity The emission of energetic particles and/or radiation during 

radioactive decay.

Radionuclide A radioactive nuclide. (A nuclide is a species of atoms characterized by the number of neutrons and protons in its nucleus.)

Recharge The process involved whereby infiltration reaches the saturated 

zone. Also the amount of water added.

Residence time In ground water, the length of time water remains underground before it is extracted or discharged.

Saline water Salty water. Classified by the dissolved solids concentration 

in water.

Sandstone A sedimentary rock composed of abundant rounded or angular 

fragments of sand set in a fine-grained matrix (silt or clay) and more or less 

firmly united by a cementing material.

Saturated The condition in which the pores of a material are filled with 

water.

Secondary Maximum Contaminant Level (SMCL) Maximum level established by the U.S. Environmental Protection Agency for contaminants that 

can adversely affect the odor or appearance of water and may result in discontinuation of use of the water. SMCL’s are nonenforceable, generally nonhealth-based standards that are related to the aesthetics of water use.

Secondary permeability The permeability developed in a rock after its 

deposition, through such processes as weathering and fracturing.

Secondary porosity The porosity developed in a rock after its deposition, 

through such processes as dissolution or fracturing.

Sedimentary rock Rocks resulting from the consolidation of loose sediment that has accumulated in layers. Examples of sedimentary rocks are 

sandstone, siltstone, limestone, and shale.

Semiconfining unit Unit that may transmit some water to and from adjacent aquifers.

Shale A fine-grained sedimentary rock, formed by the consolidation of 

clay, silt, or mud.

Sill A tabular igneous intrusion that parallels the bedding of the surrounding sedimentary or metamorphic rock.

Solution opening An opening in a rock material resulting from the dissolution of calcium carbonate in limestone or chalk.

Spring Any natural discharge of water from rock or soil onto the land 

surface or into a surface-water body.

Stratigraphic column The vertical (or chronological) sequence of rock 

units portrayed in a column from oldest (bottom) to youngest (top). See 

figure 4.

Structural feature A feature produced by deformation or displacement of 

the rocks, such as a fold or fault.

Surface water Water on the Earth’s surface.

Syncline A fold in which the strata dip toward the axis. After erosion, the 

youngest beds are exposed in the central core of the fold. 

Unconfined Said of ground water that has a water table; the water is not 

confined under pressure.

Unconfined aquifer An aquifer in which the water table is exposed to the 

atmosphere through openings in the overlying materials.

Unconsolidated aquifer An aquifer composed of material that is loosely 

arranged or whose particles are not cemented together, such as sands and 

gravels.

Unsaturated The condition in which the pores of a material contain at least 

some air.

Water table The top of the water surface in the saturated zone of an unconfined aquifer.

Water year The 12-month period, October 1 through September 30, that is 

designated by the calendar year in which it ends.